Merge branch 'feat/v1472-ketones' into feat/cycle-feed-forecast-style

# Conflicts: # CHANGELOG.md
2026-11-10 21:32:18 +00:00 · 2026-11-10 19:31:31 +01:00
commit 62f4578874
@@ -34,6 +34,22 @@
  with your account and applied by the server, so the app shows the same
  order. The labs list layout accepts `categoryOrder`, and
  `GET /api/labs/overview` answers `categories` in that order. (#1349)
+- **Blood ketones, and the glucose-ketone index worked out for you.**
+  Ketones (beta-hydroxybutyrate, mmol/L) are a measurement of their own
+  now, so a ketogenic diet no longer has to live in a custom metric with
+  the index typed in by hand beside it. Choose "Blood ketones" when you
+  add a measurement and type the glucose from the same fingerstick into
+  the field below: both readings are saved together with one time, or
+  neither is. The glucose-ketone index is glucose in mmol/L divided by
+  ketones, taken from the glucose reading at the same time or, failing
+  that, the nearest one within 15 minutes. It is never stored, so it
+  follows any reading you edit or delete. It shows under the chart on the
+  new Ketones page, in the day view, and beside the ketones in the doctor
+  report and the clinician share; the FHIR export carries the ketone
+  readings under LOINC 104816-4. Values are shown as recorded, with no
+  band and no verdict. `GET /api/measurements/series` takes
+  `kind=ketones` and `kind=glucoseKetoneIndex`, and `GET /api/day/{date}`
+  carries `glucoseKetoneIndex`. Migration `0496_blood_ketones`. (#1367)

 ### Fixed

@@ -4672,6 +4672,8 @@ paths:
              - restingHeartRate
              - heartRateVariability
              - vo2Max
+              - ketones
+              - glucoseKetoneIndex
          required: true
        - in: query
          name: days
@@ -4811,6 +4813,7 @@ paths:
              - TRAINING_READINESS
              - ACUTE_TRAINING_LOAD
              - BASAL_ENERGY_BURNED
+              - BLOOD_KETONES
        - in: query
          name: from
          schema:
@@ -5736,6 +5739,7 @@ paths:
              - TRAINING_READINESS
              - ACUTE_TRAINING_LOAD
              - BASAL_ENERGY_BURNED
+              - BLOOD_KETONES
            description: The metric.
          required: true
          description: The metric.
@@ -5866,6 +5870,7 @@ paths:
              - TRAINING_READINESS
              - ACUTE_TRAINING_LOAD
              - BASAL_ENERGY_BURNED
+              - BLOOD_KETONES
            description: The metric.
          required: true
          description: The metric.
@@ -28773,7 +28778,7 @@ components:
              type: number
              const: 2
            leaves:
-              maxItems: 111
+              maxItems: 112
              type: array
              items:
                type: string
@@ -28835,7 +28840,7 @@ components:
              type: number
              const: 2
            leaves:
-              maxItems: 111
+              maxItems: 112
              type: array
              items:
                type: string
@@ -29715,6 +29720,7 @@ components:
            - TRAINING_READINESS
            - ACUTE_TRAINING_LOAD
            - BASAL_ENERGY_BURNED
+            - BLOOD_KETONES
        value:
          type: number
        measuredAt:
@@ -31449,6 +31455,7 @@ components:
            - TRAINING_READINESS
            - ACUTE_TRAINING_LOAD
            - BASAL_ENERGY_BURNED
+            - BLOOD_KETONES
        biomarkerId:
          type: string
          minLength: 1
@@ -31948,7 +31955,7 @@ components:
          type: number
          const: 2
        leaves:
-          maxItems: 111
+          maxItems: 112
          type: array
          items:
            type: string
@@ -32593,7 +32600,7 @@ components:
              - order
        tiles:
          minItems: 1
-          maxItems: 63
+          maxItems: 64
          type: array
          items:
            type: object
@@ -32649,6 +32656,7 @@ components:
                  - audio-events
                  - daylight
                  - blood-glucose
+                  - ketones
                  - skin-temperature
                  - wrist-temperature
                  - mood
@@ -33151,6 +33159,7 @@ components:
        - TRAINING_READINESS
        - ACUTE_TRAINING_LOAD
        - BASAL_ENERGY_BURNED
+        - BLOOD_KETONES
      description: DB-stored measurement category. v1.4.23 added 7 Apple Health values (HRV, resting HR, active energy,
        flights, walking/running distance, VO2 max, body temperature).
    InsightsSettingsPutRequest:
@@ -37697,6 +37706,7 @@ components:
            - scoreSleep
            - scoreStress
            - scoreStrain
+            - bloodKetones
          description: Which chart's overlays are being written. Closed enum.
        prefs:
          type: object
@@ -37886,6 +37896,7 @@ components:
              - scoreSleep
              - scoreStress
              - scoreStrain
+              - bloodKetones
          additionalProperties:
            type: object
            properties:
@@ -38858,7 +38869,7 @@ components:
                additionalProperties: false
            tiles:
              minItems: 1
-              maxItems: 63
+              maxItems: 64
              type: array
              items:
                type: object
@@ -38914,6 +38925,7 @@ components:
                      - audio-events
                      - daylight
                      - blood-glucose
+                      - ketones
                      - skin-temperature
                      - wrist-temperature
                      - mood
@@ -42723,6 +42735,7 @@ components:
                  - TRAINING_READINESS
                  - ACUTE_TRAINING_LOAD
                  - BASAL_ENERGY_BURNED
+                  - BLOOD_KETONES
              value:
                type: number
              valueMin:
@@ -43491,6 +43504,7 @@ components:
                            - TRAINING_READINESS
                            - ACUTE_TRAINING_LOAD
                            - BASAL_ENERGY_BURNED
+                            - BLOOD_KETONES
                        - type: "null"
                    biomarkerName:
                      anyOf:
@@ -46089,6 +46103,7 @@ components:
                  - TRAINING_READINESS
                  - ACUTE_TRAINING_LOAD
                  - BASAL_ENERGY_BURNED
+                  - BLOOD_KETONES
              dateKey:
                type: string
                pattern: ^\d{4}-\d{2}-\d{2}$
@@ -47289,6 +47304,7 @@ components:
                      - TRAINING_READINESS
                      - ACUTE_TRAINING_LOAD
                      - BASAL_ENERGY_BURNED
+                      - BLOOD_KETONES
                  - type: "null"
              intervalDays:
                anyOf:
@@ -47515,6 +47531,7 @@ components:
                  - TRAINING_READINESS
                  - ACUTE_TRAINING_LOAD
                  - BASAL_ENERGY_BURNED
+                  - BLOOD_KETONES
              metricSlot:
                type:
                  - string
@@ -51039,10 +51056,12 @@ components:
            - restingHeartRate
            - heartRateVariability
            - vo2Max
+            - ketones
+            - glucoseKetoneIndex
        unit:
          type: string
          description: Resolved unit token for `value`. `glucose` follows the user's mg/dL|mmol/L preference; `sleep` is `h`
-            (per-night time-asleep in hours).
+            (per-night time-asleep in hours); `ketones` is `mmol/L`; `glucoseKetoneIndex` is `ratio`.
        points:
          type: array
          items:
@@ -51089,6 +51108,31 @@ components:
                type:
                  - number
                  - "null"
+              gki:
+                description: "#1367 — for `kind=glucoseKetoneIndex` only: the readings the index was computed from. `id` and `at` are
+                  the ketone reading's. Absent for every other kind."
+                type: object
+                properties:
+                  glucoseId:
+                    type: string
+                    description: The paired glucose reading's id.
+                  glucoseAt:
+                    type: string
+                    format: date-time
+                    pattern: ^(?:(?:\d\d[2468][048]|\d\d[13579][26]|\d\d0[48]|[02468][048]00|[13579][26]00)-02-29|\d{4}-(?:(?:0[13578]|1[02])-(?:0[1-9]|[12]\d|3[01])|(?:0[469]|11)-(?:0[1-9]|[12]\d|30)|(?:02)-(?:0[1-9]|1\d|2[0-8])))T(?:(?:[01]\d|2[0-3]):[0-5]\d:[0-5]\d(?:\.\d+)?(?:Z|([+-](?:[01]\d|2[0-3]):[0-5]\d)))$
+                    description: The paired glucose reading's timestamp.
+                  glucoseMmol:
+                    type: number
+                    description: The paired glucose in mmol/L, one decimal.
+                  ketonesMmol:
+                    type: number
+                    description: The ketone reading (beta-hydroxybutyrate), mmol/L.
+                required:
+                  - glucoseId
+                  - glucoseAt
+                  - glucoseMmol
+                  - ketonesMmol
+                additionalProperties: false
            required:
              - id
              - at
@@ -51146,7 +51190,10 @@ components:
        ring recording every minute; a cuff, a fingerstick meter or a few readings a night stay raw). A bucket carries
        the mean as `value` and otherwise has the shape of a reading of its kind; a `pulse` bucket also carries its
        range as `valueMin` / `valueMax`, and a `glucose` bucket is converted to the user's unit like a raw reading.
-        `stats` is always computed over the underlying readings, never over the buckets."
+        `stats` is always computed over the underlying readings, never over the buckets. `glucoseKetoneIndex` (#1367) is
+        derived at read time, never stored: one point per ketone reading above zero that has a glucose reading at the
+        same instant or, failing that, the nearest one within 15 minutes either side; value = glucose (mmol/L, from
+        mg/dL by 18.0182) / ketones (mmol/L), one decimal. Draw it as given; do not recompute it."
    TrendVerdict:
      type: object
      properties:
@@ -53832,6 +53879,7 @@ components:
            - TRAINING_READINESS
            - ACUTE_TRAINING_LOAD
            - BASAL_ENERGY_BURNED
+            - BLOOD_KETONES
        date:
          type: string
          format: date
@@ -54112,6 +54160,7 @@ components:
            - TRAINING_READINESS
            - ACUTE_TRAINING_LOAD
            - BASAL_ENERGY_BURNED
+            - BLOOD_KETONES
        from:
          type: string
          format: date
@@ -64561,7 +64610,7 @@ components:
            additionalProperties: false
        tiles:
          minItems: 1
-          maxItems: 63
+          maxItems: 64
          type: array
          items:
            type: object
@@ -64617,6 +64666,7 @@ components:
                  - audio-events
                  - daylight
                  - blood-glucose
+                  - ketones
                  - skin-temperature
                  - wrist-temperature
                  - mood
@@ -88230,6 +88280,7 @@ components:
              - scoreSleep
              - scoreStress
              - scoreStrain
+              - bloodKetones
          additionalProperties:
            type: object
            properties:
@@ -88496,6 +88547,7 @@ components:
              - scoreSleep
              - scoreStress
              - scoreStrain
+              - bloodKetones
          additionalProperties:
            type: object
            properties:
@@ -93870,6 +93922,14 @@ components:
          type: array
          items:
            $ref: "#/components/schemas/DayValue"
+        glucoseKetoneIndex:
+          description: "#1367 — the day's glucose-ketone index, oldest first: glucose (mmol/L) over ketones (mmol/L) for each
+            ketone reading above zero with a glucose reading at the same instant or within 15 minutes either side.
+            Computed at read time; show it as given. Absent when the day has none, when either reading type is hidden
+            from the caller, and on older servers."
+          type: array
+          items:
+            $ref: "#/components/schemas/DayGlucoseKetoneIndex"
        events:
          type: array
          items:
@@ -94074,6 +94134,43 @@ components:
        - source
        - band
      additionalProperties: false
+    DayGlucoseKetoneIndex:
+      type: object
+      properties:
+        at:
+          type: string
+          format: date-time
+          pattern: ^(?:(?:\d\d[2468][048]|\d\d[13579][26]|\d\d0[48]|[02468][048]00|[13579][26]00)-02-29|\d{4}-(?:(?:0[13578]|1[02])-(?:0[1-9]|[12]\d|3[01])|(?:0[469]|11)-(?:0[1-9]|[12]\d|30)|(?:02)-(?:0[1-9]|1\d|2[0-8])))T(?:(?:[01]\d|2[0-3]):[0-5]\d:[0-5]\d(?:\.\d+)?(?:Z|([+-](?:[01]\d|2[0-3]):[0-5]\d)))$
+          description: The ketone reading's instant.
+        value:
+          type: number
+          description: The index, to one decimal.
+        ketoneId:
+          type: string
+          description: The ketone reading's id.
+        glucoseId:
+          type: string
+          description: The paired glucose reading's id.
+        glucoseAt:
+          type: string
+          format: date-time
+          pattern: ^(?:(?:\d\d[2468][048]|\d\d[13579][26]|\d\d0[48]|[02468][048]00|[13579][26]00)-02-29|\d{4}-(?:(?:0[13578]|1[02])-(?:0[1-9]|[12]\d|3[01])|(?:0[469]|11)-(?:0[1-9]|[12]\d|30)|(?:02)-(?:0[1-9]|1\d|2[0-8])))T(?:(?:[01]\d|2[0-3]):[0-5]\d:[0-5]\d(?:\.\d+)?(?:Z|([+-](?:[01]\d|2[0-3]):[0-5]\d)))$
+          description: The paired glucose reading's instant.
+        ketonesMmol:
+          type: number
+          description: Beta-hydroxybutyrate, mmol/L.
+        glucoseMmol:
+          type: number
+          description: The paired glucose in mmol/L, one decimal.
+      required:
+        - at
+        - value
+        - ketoneId
+        - glucoseId
+        - glucoseAt
+        - ketonesMmol
+        - glucoseMmol
+      additionalProperties: false
    DayEvent:
      type: object
      properties:
@@ -163,6 +163,7 @@ hand-authored.
 | `RESPIRATORY_RATE`              | count/min            |
 | `OXYGEN_SATURATION`             | percent (0–100)      |
 | `BLOOD_GLUCOSE`                 | mg/dL                |
+| `BLOOD_KETONES`                 | mmol/L               |
 | `BODY_FAT`                      | percent (0–100)      |
 | `FAT_MASS`                      | kg                   |
 | `FAT_FREE_MASS`                 | kg                   |
@@ -813,6 +813,10 @@
    "typeSleep": "Schlaf",
    "typeSteps": "Schritte",
    "typeBloodGlucose": "Blutzucker",
+    "typeBloodKetones": "Blutketone",
+    "glucoseKetoneIndex": "Glukose-Keton-Index",
+    "pairedGlucoseLabel": "Blutzucker aus derselben Messung ({unit})",
+    "pairedGlucoseHint": "Wird als eigener Blutzuckerwert mit derselben Uhrzeit gespeichert; aus dem Paar ergibt sich der Glukose-Keton-Index.",
    "typeTotalBodyWater": "Gesamtkörperwasser",
    "typeBoneMass": "Knochenmasse",
    "typeOxygenSaturation": "Sauerstoffsättigung",
@@ -4002,6 +4006,23 @@
      }
    },
    "navBloodGlucose": "Glukose",
+    "navBloodKetones": "Ketone",
+    "bloodKetones": {
+      "title": "Blutketone",
+      "description": "Deine Beta-Hydroxybutyrat-Werte im Zeitverlauf, in {unit}.",
+      "chartTitle": "Blutketone",
+      "emptyState": {
+        "title": "Noch keine Ketonwerte",
+        "description": "Ketonwerte erscheinen hier, sobald du einen erfasst, allein oder mit dem Blutzucker aus demselben Fingerstich.",
+        "cta": "Ketone erfassen"
+      },
+      "gki": {
+        "description": "Blutzucker geteilt durch Ketone, für jeden Ketonwert mit einem Blutzuckerwert innerhalb von 15 Minuten.",
+        "emptyTitle": "Noch kein Index",
+        "emptyDescription": "Er erscheint, sobald zu einem Ketonwert ein Blutzuckerwert zur selben Zeit oder innerhalb von 15 Minuten vorliegt.",
+        "latest": "Zuletzt {value}: Blutzucker {glucose} {unit} durch Ketone {ketones} {unit}, {date}."
+      }
+    },
    "totalBodyWater": {
      "title": "Gesamtkörperwasser",
      "description": "Dein Gesamtkörperwasser im Zeitverlauf, in Kilogramm.",
@@ -13689,6 +13710,10 @@
    "valuesAllFew": "Alle {count} Werte",
    "valuesAllOther": "Alle {count} Werte",
    "valuesFewer": "Weniger Werte",
+    "gkiPair": "Blutzucker {glucose} / Ketone {ketones}",
+    "gkiCountOne": "Letzter von {count}",
+    "gkiCountFew": "Letzter von {count}",
+    "gkiCountOther": "Letzter von {count}",
    "countEntriesOne": "1 Eintrag",
    "countEntriesFew": "{count} Einträge",
    "countEntriesOther": "{count} Einträge",
@@ -813,6 +813,10 @@
    "typeSleep": "Sleep",
    "typeSteps": "Steps",
    "typeBloodGlucose": "Blood glucose",
+    "typeBloodKetones": "Blood ketones",
+    "glucoseKetoneIndex": "Glucose-ketone index",
+    "pairedGlucoseLabel": "Glucose from the same reading ({unit})",
+    "pairedGlucoseHint": "Saved as its own glucose reading at the same time; the glucose-ketone index is worked out from the pair.",
    "typeTotalBodyWater": "Total body water",
    "typeBoneMass": "Bone mass",
    "typeOxygenSaturation": "Oxygen saturation",
@@ -4002,6 +4006,23 @@
      }
    },
    "navBloodGlucose": "Glucose",
+    "navBloodKetones": "Ketones",
+    "bloodKetones": {
+      "title": "Blood Ketones",
+      "description": "Your beta-hydroxybutyrate readings over time, in {unit}.",
+      "chartTitle": "Blood ketones",
+      "emptyState": {
+        "title": "No ketone readings yet",
+        "description": "Ketone readings appear here once you log one, on its own or with the glucose from the same fingerstick.",
+        "cta": "Log ketones"
+      },
+      "gki": {
+        "description": "Glucose divided by ketones, for each ketone reading with a glucose reading within 15 minutes.",
+        "emptyTitle": "No index yet",
+        "emptyDescription": "It appears once a ketone reading has a glucose reading taken at the same time or within 15 minutes.",
+        "latest": "Latest {value}: glucose {glucose} {unit} over ketones {ketones} {unit}, {date}."
+      }
+    },
    "totalBodyWater": {
      "title": "Total Body Water",
      "description": "Your total body water over time, in kilograms.",
@@ -13689,6 +13710,10 @@
    "valuesAllFew": "All {count} values",
    "valuesAllOther": "All {count} values",
    "valuesFewer": "Fewer values",
+    "gkiPair": "Glucose {glucose} / ketones {ketones}",
+    "gkiCountOne": "Latest of {count}",
+    "gkiCountFew": "Latest of {count}",
+    "gkiCountOther": "Latest of {count}",
    "countEntriesOne": "1 entry",
    "countEntriesFew": "{count} entries",
    "countEntriesOther": "{count} entries",
@@ -813,6 +813,10 @@
    "typeSleep": "Sueño",
    "typeSteps": "Pasos",
    "typeBloodGlucose": "Glucemia",
+    "typeBloodKetones": "Cetonas en sangre",
+    "glucoseKetoneIndex": "Índice glucosa-cetonas",
+    "pairedGlucoseLabel": "Glucosa de la misma medición ({unit})",
+    "pairedGlucoseHint": "Se guarda como una lectura de glucosa propia con la misma hora; el índice glucosa-cetonas se calcula a partir del par.",
    "typeTotalBodyWater": "Agua corporal total",
    "typeBoneMass": "Masa ósea",
    "typeOxygenSaturation": "Saturación de oxígeno",
@@ -4002,6 +4006,23 @@
      }
    },
    "navBloodGlucose": "Glucosa",
+    "navBloodKetones": "Cetonas",
+    "bloodKetones": {
+      "title": "Cetonas en sangre",
+      "description": "Tus lecturas de beta-hidroxibutirato en el tiempo, en {unit}.",
+      "chartTitle": "Cetonas en sangre",
+      "emptyState": {
+        "title": "Aún no hay lecturas de cetonas",
+        "description": "Las lecturas de cetonas aparecen aquí cuando registras una, sola o con la glucosa del mismo pinchazo.",
+        "cta": "Registrar cetonas"
+      },
+      "gki": {
+        "description": "Glucosa dividida por cetonas, para cada lectura de cetonas con una de glucosa en un margen de 15 minutos.",
+        "emptyTitle": "Aún no hay índice",
+        "emptyDescription": "Aparece cuando una lectura de cetonas tiene una de glucosa tomada a la misma hora o en un margen de 15 minutos.",
+        "latest": "Último {value}: glucosa {glucose} {unit} entre cetonas {ketones} {unit}, {date}."
+      }
+    },
    "totalBodyWater": {
      "title": "Agua corporal total",
      "description": "Tu agua corporal total en el tiempo, en kilogramos.",
@@ -13689,6 +13710,10 @@
    "valuesAllFew": "Los {count} valores",
    "valuesAllOther": "Los {count} valores",
    "valuesFewer": "Menos valores",
+    "gkiPair": "Glucosa {glucose} / cetonas {ketones}",
+    "gkiCountOne": "Último de {count}",
+    "gkiCountFew": "Último de {count}",
+    "gkiCountOther": "Último de {count}",
    "countEntriesOne": "1 entrada",
    "countEntriesFew": "{count} entradas",
    "countEntriesOther": "{count} entradas",
@@ -813,6 +813,10 @@
    "typeSleep": "Sommeil",
    "typeSteps": "Pas",
    "typeBloodGlucose": "Glycémie",
+    "typeBloodKetones": "Cétones sanguines",
+    "glucoseKetoneIndex": "Indice glucose-cétones",
+    "pairedGlucoseLabel": "Glycémie de la même mesure ({unit})",
+    "pairedGlucoseHint": "Enregistrée comme un relevé de glycémie à la même heure ; l’indice glucose-cétones est calculé à partir de la paire.",
    "typeTotalBodyWater": "Eau corporelle totale",
    "typeBoneMass": "Masse osseuse",
    "typeOxygenSaturation": "Saturation en oxygène",
@@ -4002,6 +4006,23 @@
      }
    },
    "navBloodGlucose": "Glucose",
+    "navBloodKetones": "Cétones",
+    "bloodKetones": {
+      "title": "Cétones sanguines",
+      "description": "Vos relevés de bêta-hydroxybutyrate au fil du temps, en {unit}.",
+      "chartTitle": "Cétones sanguines",
+      "emptyState": {
+        "title": "Pas encore de relevé de cétones",
+        "description": "Les relevés de cétones apparaissent ici dès que vous en saisissez un, seul ou avec la glycémie de la même piqûre.",
+        "cta": "Enregistrer les cétones"
+      },
+      "gki": {
+        "description": "Glycémie divisée par les cétones, pour chaque relevé de cétones accompagné d’une glycémie à 15 minutes près.",
+        "emptyTitle": "Pas encore d’indice",
+        "emptyDescription": "Il apparaît dès qu’un relevé de cétones a une glycémie prise au même moment ou à 15 minutes près.",
+        "latest": "Dernier {value} : glycémie {glucose} {unit} sur cétones {ketones} {unit}, {date}."
+      }
+    },
    "totalBodyWater": {
      "title": "Eau corporelle totale",
      "description": "Votre eau corporelle totale au fil du temps, en kilogrammes.",
@@ -13689,6 +13710,10 @@
    "valuesAllFew": "Les {count} valeurs",
    "valuesAllOther": "Les {count} valeurs",
    "valuesFewer": "Moins de valeurs",
+    "gkiPair": "Glycémie {glucose} / cétones {ketones}",
+    "gkiCountOne": "Dernier sur {count}",
+    "gkiCountFew": "Dernier sur {count}",
+    "gkiCountOther": "Dernier sur {count}",
    "countEntriesOne": "{count} entrée",
    "countEntriesFew": "{count} entrées",
    "countEntriesOther": "{count} entrées",
@@ -813,6 +813,10 @@
    "typeSleep": "Sonno",
    "typeSteps": "Passi",
    "typeBloodGlucose": "Glicemia",
+    "typeBloodKetones": "Chetoni nel sangue",
+    "glucoseKetoneIndex": "Indice glucosio-chetoni",
+    "pairedGlucoseLabel": "Glicemia della stessa misurazione ({unit})",
+    "pairedGlucoseHint": "Salvata come lettura di glicemia a sé con lo stesso orario; l’indice glucosio-chetoni si ricava dalla coppia.",
    "typeTotalBodyWater": "Acqua corporea totale",
    "typeBoneMass": "Massa ossea",
    "typeOxygenSaturation": "Saturazione di ossigeno",
@@ -4002,6 +4006,23 @@
      }
    },
    "navBloodGlucose": "Glucosio",
+    "navBloodKetones": "Chetoni",
+    "bloodKetones": {
+      "title": "Chetoni nel sangue",
+      "description": "Le tue letture di beta-idrossibutirrato nel tempo, in {unit}.",
+      "chartTitle": "Chetoni nel sangue",
+      "emptyState": {
+        "title": "Ancora nessuna lettura di chetoni",
+        "description": "Le letture di chetoni appaiono qui quando ne registri una, da sola o con la glicemia della stessa puntura.",
+        "cta": "Registra i chetoni"
+      },
+      "gki": {
+        "description": "Glicemia divisa per i chetoni, per ogni lettura di chetoni con una glicemia entro 15 minuti.",
+        "emptyTitle": "Ancora nessun indice",
+        "emptyDescription": "Compare quando una lettura di chetoni ha una glicemia presa allo stesso momento o entro 15 minuti.",
+        "latest": "Ultimo {value}: glicemia {glucose} {unit} su chetoni {ketones} {unit}, {date}."
+      }
+    },
    "totalBodyWater": {
      "title": "Acqua corporea totale",
      "description": "La tua acqua corporea totale nel tempo, in chilogrammi.",
@@ -13689,6 +13710,10 @@
    "valuesAllFew": "Tutti i {count} valori",
    "valuesAllOther": "Tutti i {count} valori",
    "valuesFewer": "Meno valori",
+    "gkiPair": "Glicemia {glucose} / chetoni {ketones}",
+    "gkiCountOne": "Ultimo di {count}",
+    "gkiCountFew": "Ultimo di {count}",
+    "gkiCountOther": "Ultimo di {count}",
    "countEntriesOne": "1 voce",
    "countEntriesFew": "{count} voci",
    "countEntriesOther": "{count} voci",
@@ -813,6 +813,10 @@
    "typeSleep": "수면",
    "typeSteps": "걸음 수",
    "typeBloodGlucose": "혈당",
+    "typeBloodKetones": "혈중 케톤",
+    "glucoseKetoneIndex": "포도당-케톤 지수",
+    "pairedGlucoseLabel": "같은 측정의 혈당 ({unit})",
+    "pairedGlucoseHint": "같은 시각의 별도 혈당 기록으로 저장되고, 두 값으로 포도당-케톤 지수를 계산해요.",
    "typeTotalBodyWater": "체수분",
    "typeBoneMass": "골량",
    "typeOxygenSaturation": "산소포화도",
@@ -4002,6 +4006,23 @@
      }
    },
    "navBloodGlucose": "혈당",
+    "navBloodKetones": "케톤",
+    "bloodKetones": {
+      "title": "혈중 케톤",
+      "description": "시간에 따른 베타-하이드록시부티르산 측정값이에요({unit}).",
+      "chartTitle": "혈중 케톤",
+      "emptyState": {
+        "title": "아직 케톤 측정값이 없어요",
+        "description": "케톤을 단독으로 또는 같은 채혈의 혈당과 함께 기록하면 여기에 측정값이 나타나요.",
+        "cta": "케톤 기록"
+      },
+      "gki": {
+        "description": "15분 이내에 혈당 측정값이 있는 케톤 측정마다 혈당을 케톤으로 나눈 값이에요.",
+        "emptyTitle": "아직 지수가 없어요",
+        "emptyDescription": "케톤 측정과 같은 시각이나 15분 이내에 잰 혈당이 있으면 나타나요.",
+        "latest": "최근 {value}: 혈당 {glucose} {unit} ÷ 케톤 {ketones} {unit}, {date}."
+      }
+    },
    "totalBodyWater": {
      "title": "총 체수분",
      "description": "시간에 따른 총 체수분이에요(kg).",
@@ -13689,6 +13710,10 @@
    "valuesAllFew": "수치 {count}개 모두",
    "valuesAllOther": "수치 {count}개 모두",
    "valuesFewer": "수치 줄여 보기",
+    "gkiPair": "혈당 {glucose} / 케톤 {ketones}",
+    "gkiCountOne": "{count}개 중 최근",
+    "gkiCountFew": "{count}개 중 최근",
+    "gkiCountOther": "{count}개 중 최근",
    "countEntriesOne": "기록 1개",
    "countEntriesFew": "기록 {count}개",
    "countEntriesOther": "기록 {count}개",
@@ -813,6 +813,10 @@
    "typeSleep": "Slaap",
    "typeSteps": "Stappen",
    "typeBloodGlucose": "Bloedglucose",
+    "typeBloodKetones": "Bloedketonen",
+    "glucoseKetoneIndex": "Glucose-ketonindex",
+    "pairedGlucoseLabel": "Glucose uit dezelfde meting ({unit})",
+    "pairedGlucoseHint": "Wordt als eigen glucosemeting met hetzelfde tijdstip opgeslagen; uit het paar volgt de glucose-ketonindex.",
    "typeTotalBodyWater": "Totaal lichaamswater",
    "typeBoneMass": "Botmassa",
    "typeOxygenSaturation": "Zuurstofsaturatie",
@@ -4002,6 +4006,23 @@
      }
    },
    "navBloodGlucose": "Glucose",
+    "navBloodKetones": "Ketonen",
+    "bloodKetones": {
+      "title": "Bloedketonen",
+      "description": "Je bèta-hydroxybutyraatmetingen in de loop van de tijd, in {unit}.",
+      "chartTitle": "Bloedketonen",
+      "emptyState": {
+        "title": "Nog geen ketonmetingen",
+        "description": "Ketonmetingen verschijnen hier zodra je er een vastlegt, los of met de glucose uit dezelfde vingerprik.",
+        "cta": "Ketonen vastleggen"
+      },
+      "gki": {
+        "description": "Glucose gedeeld door ketonen, voor elke ketonmeting met een glucosemeting binnen 15 minuten.",
+        "emptyTitle": "Nog geen index",
+        "emptyDescription": "Hij verschijnt zodra een ketonmeting een glucosemeting op hetzelfde moment of binnen 15 minuten heeft.",
+        "latest": "Laatst {value}: glucose {glucose} {unit} gedeeld door ketonen {ketones} {unit}, {date}."
+      }
+    },
    "totalBodyWater": {
      "title": "Totaal lichaamswater",
      "description": "Je totale lichaamswater in de loop van de tijd, in kilogram.",
@@ -13689,6 +13710,10 @@
    "valuesAllFew": "Alle {count} waarden",
    "valuesAllOther": "Alle {count} waarden",
    "valuesFewer": "Minder waarden",
+    "gkiPair": "Glucose {glucose} / ketonen {ketones}",
+    "gkiCountOne": "Laatste van {count}",
+    "gkiCountFew": "Laatste van {count}",
+    "gkiCountOther": "Laatste van {count}",
    "countEntriesOne": "1 registratie",
    "countEntriesFew": "{count} registraties",
    "countEntriesOther": "{count} registraties",
@@ -813,6 +813,10 @@
    "typeSleep": "Sen",
    "typeSteps": "Kroki",
    "typeBloodGlucose": "Glikemia",
+    "typeBloodKetones": "Ketony we krwi",
+    "glucoseKetoneIndex": "Indeks glukozowo-ketonowy",
+    "pairedGlucoseLabel": "Glukoza z tego samego pomiaru ({unit})",
+    "pairedGlucoseHint": "Zapisywana jako osobny odczyt glukozy z tą samą godziną; z tej pary obliczany jest indeks glukozowo-ketonowy.",
    "typeTotalBodyWater": "Całkowita woda w organizmie",
    "typeBoneMass": "Masa kostna",
    "typeOxygenSaturation": "Saturacja tlenem",
@@ -4002,6 +4006,23 @@
      }
    },
    "navBloodGlucose": "Glukoza",
+    "navBloodKetones": "Ketony",
+    "bloodKetones": {
+      "title": "Ketony we krwi",
+      "description": "Twoje odczyty beta-hydroksymaślanu w czasie, w {unit}.",
+      "chartTitle": "Ketony we krwi",
+      "emptyState": {
+        "title": "Brak jeszcze odczytów ketonów",
+        "description": "Odczyty ketonów pojawią się tutaj po zapisaniu jednego, osobno lub z glukozą z tego samego nakłucia.",
+        "cta": "Zapisz ketony"
+      },
+      "gki": {
+        "description": "Glukoza podzielona przez ketony, dla każdego odczytu ketonów z odczytem glukozy w ciągu 15 minut.",
+        "emptyTitle": "Brak jeszcze indeksu",
+        "emptyDescription": "Pojawi się, gdy do odczytu ketonów będzie odczyt glukozy z tej samej chwili lub w ciągu 15 minut.",
+        "latest": "Ostatnio {value}: glukoza {glucose} {unit} przez ketony {ketones} {unit}, {date}."
+      }
+    },
    "totalBodyWater": {
      "title": "Całkowita woda w organizmie",
      "description": "Twoja całkowita woda w organizmie w czasie, w kilogramach.",
@@ -13689,6 +13710,10 @@
    "valuesAllFew": "Wszystkie {count} wartości",
    "valuesAllOther": "Wszystkie {count} wartości",
    "valuesFewer": "Mniej wartości",
+    "gkiPair": "Glukoza {glucose} / ketony {ketones}",
+    "gkiCountOne": "Ostatni z {count}",
+    "gkiCountFew": "Ostatni z {count}",
+    "gkiCountOther": "Ostatni z {count}",
    "countEntriesOne": "1 wpis",
    "countEntriesFew": "{count} wpisy",
    "countEntriesOther": "{count} wpisów",
@@ -813,6 +813,10 @@
    "typeSleep": "Sono",
    "typeSteps": "Passos",
    "typeBloodGlucose": "Glicemia",
+    "typeBloodKetones": "Cetonas no sangue",
+    "glucoseKetoneIndex": "Índice glicose-cetona",
+    "pairedGlucoseLabel": "Glicose da mesma medição ({unit})",
+    "pairedGlucoseHint": "Salva como uma leitura de glicose própria no mesmo horário; o índice glicose-cetona é calculado a partir do par.",
    "typeTotalBodyWater": "Água corporal total",
    "typeBoneMass": "Massa óssea",
    "typeOxygenSaturation": "Saturação de oxigênio",
@@ -4002,6 +4006,23 @@
      }
    },
    "navBloodGlucose": "Glicose",
+    "navBloodKetones": "Cetonas",
+    "bloodKetones": {
+      "title": "Cetonas no sangue",
+      "description": "Suas leituras de beta-hidroxibutirato ao longo do tempo, em {unit}.",
+      "chartTitle": "Cetonas no sangue",
+      "emptyState": {
+        "title": "Ainda não há leituras de cetonas",
+        "description": "As leituras de cetonas aparecem aqui assim que você registra uma, sozinha ou com a glicose da mesma picada.",
+        "cta": "Registrar cetonas"
+      },
+      "gki": {
+        "description": "Glicose dividida pelas cetonas, para cada leitura de cetonas com uma de glicose em até 15 minutos.",
+        "emptyTitle": "Ainda não há índice",
+        "emptyDescription": "Ele aparece quando uma leitura de cetonas tem uma de glicose feita no mesmo horário ou em até 15 minutos.",
+        "latest": "Último {value}: glicose {glucose} {unit} sobre cetonas {ketones} {unit}, {date}."
+      }
+    },
    "totalBodyWater": {
      "title": "Água Corporal Total",
      "description": "Sua água corporal total ao longo do tempo, em quilogramas.",
@@ -13689,6 +13710,10 @@
    "valuesAllFew": "Todos os {count} valores",
    "valuesAllOther": "Todos os {count} valores",
    "valuesFewer": "Menos valores",
+    "gkiPair": "Glicose {glucose} / cetonas {ketones}",
+    "gkiCountOne": "Último de {count}",
+    "gkiCountFew": "Último de {count}",
+    "gkiCountOther": "Último de {count}",
    "countEntriesOne": "{count} entrada",
    "countEntriesFew": "{count} entradas",
    "countEntriesOther": "{count} entradas",
@@ -813,6 +813,10 @@
    "typeSleep": "Сон",
    "typeSteps": "Шаги",
    "typeBloodGlucose": "Глюкоза крови",
+    "typeBloodKetones": "Кетоны в крови",
+    "glucoseKetoneIndex": "Глюкозо-кетоновый индекс",
+    "pairedGlucoseLabel": "Глюкоза из того же измерения ({unit})",
+    "pairedGlucoseHint": "Сохраняется как отдельное измерение глюкозы с тем же временем; по этой паре рассчитывается глюкозо-кетоновый индекс.",
    "typeTotalBodyWater": "Общая вода в организме",
    "typeBoneMass": "Костная масса",
    "typeOxygenSaturation": "Насыщение кислородом",
@@ -4002,6 +4006,23 @@
      }
    },
    "navBloodGlucose": "Глюкоза",
+    "navBloodKetones": "Кетоны",
+    "bloodKetones": {
+      "title": "Кетоны в крови",
+      "description": "Ваши измерения бета-гидроксибутирата в динамике, в {unit}.",
+      "chartTitle": "Кетоны в крови",
+      "emptyState": {
+        "title": "Измерений кетонов пока нет",
+        "description": "Измерения кетонов появятся здесь, как только вы запишете одно, отдельно или вместе с глюкозой из того же прокола.",
+        "cta": "Записать кетоны"
+      },
+      "gki": {
+        "description": "Глюкоза, делённая на кетоны, для каждого измерения кетонов с измерением глюкозы в пределах 15 минут.",
+        "emptyTitle": "Индекса пока нет",
+        "emptyDescription": "Он появится, когда к измерению кетонов будет измерение глюкозы в то же время или в пределах 15 минут.",
+        "latest": "Последний {value}: глюкоза {glucose} {unit} на кетоны {ketones} {unit}, {date}."
+      }
+    },
    "totalBodyWater": {
      "title": "Общая вода в организме",
      "description": "Ваша общая вода в организме в динамике, в килограммах.",
@@ -13689,6 +13710,10 @@
    "valuesAllFew": "Все {count} значения",
    "valuesAllOther": "Все {count} значений",
    "valuesFewer": "Меньше значений",
+    "gkiPair": "Глюкоза {glucose} / кетоны {ketones}",
+    "gkiCountOne": "Последний из {count}",
+    "gkiCountFew": "Последний из {count}",
+    "gkiCountOther": "Последний из {count}",
    "countEntriesOne": "{count} запись",
    "countEntriesFew": "Записей: {count}",
    "countEntriesOther": "Записей: {count}",
@@ -0,0 +1,12 @@
+-- Extend `measurement_type` with blood ketones (#1367):
+--
+--   BLOOD_KETONES  <- beta-hydroxybutyrate from a blood ketone meter (mmol/L)
+--
+-- Purely additive: no existing row carries the value, and nothing in this
+-- file uses it, so the rule that a value added in a transaction cannot be used
+-- in that same transaction never comes into play. IF NOT EXISTS keeps a replay
+-- on a partially applied database harmless. Enum values cannot be dropped in
+-- PostgreSQL, so there is no down path. The glucose-ketone index is computed
+-- at read time and has no column.
+
+ALTER TYPE "measurement_type" ADD VALUE IF NOT EXISTS 'BLOOD_KETONES';
@@ -1816,6 +1816,10 @@ enum MeasurementType {
  // v1.47.1 — resting energy (#1340). Its own type beside ACTIVE_ENERGY_BURNED,
  // never folded into it and never summed with it into a total.
  BASAL_ENERGY_BURNED // kcal — HealthKit `basalEnergyBurned`, the energy the body uses at rest; cumulative, daily SUM.
+  // v1.47.2 — blood ketones (#1367). Beta-hydroxybutyrate from a fingerstick
+  // meter, typed by hand. The glucose-ketone index is derived from this and
+  // BLOOD_GLUCOSE at read time and never stored.
+  BLOOD_KETONES // mmol/L — capillary or venous beta-hydroxybutyrate (BHB); spot reading, never summed.

  @@map("measurement_type")
 }
@@ -11,7 +11,7 @@
    "components/insights/coach-panel/use-coach.ts": 1486,
    "components/insights/derived/vitals-dashboard.tsx": 1033,
    "components/insights/health-score-card.tsx": 1023,
-    "components/insights/insights-tab-strip.tsx": 1086,
+    "components/insights/insights-tab-strip.tsx": 1087,
    "components/measurements/measurement-form.tsx": 815,
    "components/medications/detail/medication-detail-tabs.tsx": 1157,
    "components/medications/medication-table.tsx": 853,
@@ -39,7 +39,7 @@
    "lib/daily/digest.ts": 1317,
    "lib/daily/load-digest.ts": 1000,
    "lib/daily/today-overview.ts": 838,
-    "lib/dashboard-layout.ts": 976,
+    "lib/dashboard-layout.ts": 977,
    "lib/dashboard/snapshot.ts": 1550,
    "lib/day/records.ts": 1174,
    "lib/export/backup-plan.ts": 838,
@@ -149,6 +149,10 @@ const ALLOWED_SQL: Record<string, string> = {
    "Selects from `unnest` of the caller's type list; `measurements` is read inside `EXISTS`, one row per type at most.",
  "lib/dashboard/summary-reads.ts::1":
    "Selects from `unnest` of the type list; `measurements` is read only inside COUNT scalar subqueries, before the fold window for a type the DAY rollups cover.",
+  "lib/measurements/read-glucose-ketone-index.ts::1":
+    "Ketone readings in the window: typed off a fingerstick meter, a few a day at most. Each one is paired with a glucose reading, so the rows themselves are needed.",
+  "lib/measurements/read-glucose-ketone-index.ts::2":
+    "Glucose rows only within 15 minutes of one of those ketone readings (`EXISTS`): a handful per fingerstick even under a sensor, never the window's glucose series.",
  "lib/dashboard/summary-reads.ts::2":
    "Selects from `generate_series` of the streak window's local days; `measurements` is read inside `EXISTS`, one row per day at most.",
 };
@@ -70,8 +70,8 @@ describe("report scope gating — structural guard", () => {
  it("reads a plausible catalogue", () => {
    // Sanity floor: a silently degraded catalogue would pass everything below
    // vacuously.
-    expect(ALL_LEAF_IDS.length).toBe(111);
-    expect(Object.keys(MEASUREMENT_LEAF_GROUP)).toHaveLength(91);
+    expect(ALL_LEAF_IDS.length).toBe(112);
+    expect(Object.keys(MEASUREMENT_LEAF_GROUP)).toHaveLength(92);
    expect(Object.keys(STRUCTURED_LEAF_GROUP)).toHaveLength(20);
  });

@@ -294,7 +294,7 @@ const UNIT_LITERAL_ALLOWLIST: Record<
    reason: "the onboarding unit picker: its options are the two units",
  },
  "components/measurements/measurement-form.tsx": {
-    lines: 11,
+    lines: 12,
    reason:
      "input parsing: canonical units of the entry table, replaced by the transform's unit at render and inverted on save",
  },
@@ -362,9 +362,9 @@ const UNIT_LITERAL_ALLOWLIST: Record<
    reason: "the legacy export endpoint's canonical storage-unit contract",
  },
  "lib/measurements/series/kinds.ts": {
-    lines: 4,
+    lines: 5,
    reason:
-      "canonical wire units; glucose is overridden to the reader's unit per request",
+      "canonical wire units; glucose is overridden to the reader's unit per request, ketones have no unit choice",
  },
  "lib/doctor-report/stat-display.ts": {
    lines: 3,
@@ -0,0 +1,39 @@
+"use client";
+
+import { Droplet } from "lucide-react";
+
+import { HealthKitMetricPage } from "@/components/insights/healthkit-metric-page";
+import { GkiCard } from "@/components/insights/ketones/gki-card";
+import { getUnitForType } from "@/lib/measurements/unit-map";
+
+/** mmol/L, from the one canonical unit table; ketones have no unit choice. */
+const KETONE_UNIT = getUnitForType("BLOOD_KETONES");
+
+/**
+ * `/insights/ketones` (#1367).
+ *
+ * Blood ketones (beta-hydroxybutyrate, mmol/L) on the generic metric
+ * scaffold, with the glucose-ketone index beneath the chart. Readings are
+ * typed off a meter, alone or together with the glucose from the same
+ * fingerstick, so the empty state offers manual entry. No band and no
+ * assessment card: what a ketone reading should be follows the plan a
+ * clinician sets, and the page shows the readings as recorded.
+ */
+export default function InsightsKetonesPage() {
+  return (
+    <HealthKitMetricPage
+      measurementType="BLOOD_KETONES"
+      insightMetric="BLOOD_KETONES"
+      chartKey="bloodKetones"
+      i18nPrefix="insights.bloodKetones"
+      color="var(--chart-3)"
+      unit={KETONE_UNIT}
+      yAxisUnit={KETONE_UNIT}
+      statFractionDigits={1}
+      emptyStateIcon={<Droplet className="size-6" />}
+      emptyStateCtaType="BLOOD_KETONES"
+      captureType="BLOOD_KETONES"
+      afterChart={<GkiCard />}
+    />
+  );
+}
@@ -261,6 +261,21 @@ export function MeasurementGroups({
                    max: show(type, stat!.max, digits),
                  })}
                />
+                {type === "BLOOD_KETONES" &&
+                report.glucoseKetoneIndex &&
+                scope.admits("BLOOD_GLUCOSE") ? (
+                  // #1367 — the index the server derived from the ketone
+                  // and glucose readings, beside the ketones; no unit.
+                  <StatRow
+                    label={t("measurements.glucoseKetoneIndex")}
+                    value={statSummary(t, "", {
+                      latest: fmtDigits(report.glucoseKetoneIndex.latest, 1),
+                      avg: fmtDigits(report.glucoseKetoneIndex.avg, 1),
+                      min: fmtDigits(report.glucoseKetoneIndex.min, 1),
+                      max: fmtDigits(report.glucoseKetoneIndex.max, 1),
+                    })}
+                  />
+                ) : null}
                {unvalidated > 0 && (
                  <p
                    className="text-muted-foreground text-xs"
@@ -0,0 +1,46 @@
+"use client";
+
+import Link from "next/link";
+
+import type { DayResponse } from "@/lib/day/contract";
+import { useFormatters, useTranslations } from "@/lib/i18n/context";
+
+type DayGki = NonNullable<DayResponse["glucoseKetoneIndex"]>[number];
+
+/**
+ * The day's glucose-ketone index (#1367), one tile beside the value tiles.
+ * Every figure is the server's: the index and the two readings it was built
+ * from. A day with one fingerstick shows its index and the pair; a day with
+ * several shows the latest index and how many there were, and the ketones page
+ * lists each. Nothing grades the number.
+ */
+export function DayGkiTile({ points }: { points: readonly DayGki[] }) {
+  const { t, tCount } = useTranslations();
+  const fmt = useFormatters();
+  const latest = points[points.length - 1];
+  if (!latest) return null;
+  return (
+    <li data-slot="day-gki" className="flex min-w-0">
+      <Link
+        href="/insights/ketones"
+        data-slot="day-value-link"
+        className="bg-muted/60 hover:bg-muted focus-visible:ring-ring/50 flex min-h-11 w-full min-w-0 flex-col rounded-lg px-3 py-2.5 transition-colors focus-visible:ring-[3px] focus-visible:outline-none"
+      >
+        <span className="text-muted-foreground truncate text-xs">
+          {t("measurements.glucoseKetoneIndex")}
+        </span>
+        <span className="truncate text-base font-semibold tabular-nums">
+          {fmt.number(latest.value, 1)}
+        </span>
+        <span className="text-muted-foreground truncate text-xs tabular-nums">
+          {points.length > 1
+            ? tCount("day.gkiCount", points.length)
+            : t("day.gkiPair", {
+                glucose: fmt.number(latest.glucoseMmol, 1),
+                ketones: fmt.number(latest.ketonesMmol, 1),
+              })}
+        </span>
+      </Link>
+    </li>
+  );
+}
@@ -29,9 +29,9 @@ import {
  type DayEvent,
  type DayEventKind,
  type DayNotable,
+  type DayResponse,
  type DayRunningItem,
  type DayRunningKind,
-  type DayValue,
 } from "@/lib/day/contract";
 import { visitKindWords } from "@/components/timeline/item-words";
 import {
@@ -62,6 +62,7 @@ import {
  WORKOUT_SPORT_KEY,
 } from "./label-keys";
 import { cycleRunningLine } from "./day-cycle-line";
+import { DayGkiTile } from "./day-gki-tile";
 import { useDayValueFormat } from "./use-day-value-format";

 /**
@@ -508,12 +509,14 @@ function ValueTile({
 }

 export function DayValues({
-  values,
+  day,
  focusTypes,
 }: {
-  values: readonly DayValue[];
+  /** The day's values and its server-derived glucose-ketone index (#1367). */
+  day: Pick<DayResponse, "values" | "glucoseKetoneIndex">;
  focusTypes: readonly string[];
 }) {
+  const { values } = day;
  const { t, tCount } = useTranslations();
  const [expanded, setExpanded] = useState(false);
  if (values.length === 0) return null;
@@ -537,6 +540,7 @@ export function DayValues({
            selected={focusKeys.has(tile.key)}
          />
        ))}
+        <DayGkiTile points={day.glucoseKetoneIndex ?? []} />
      </ul>
      {rest.length > 0 ? (
        <button
@@ -296,7 +296,7 @@ export function DayView({
            <DayRunning items={data.running} date={date} />
            {data.values.length > 0 ? (
              <div className="space-y-2.5">
-                <DayValues values={data.values} focusTypes={focusTypes} />
+                <DayValues day={data} focusTypes={focusTypes} />
                <DayNotableLines
                  notables={otherNotables}
                  labelFor={labelFor}
@@ -380,6 +380,7 @@ export const SUB_PAGE_TABS: Record<
    labelKey: "insights.navBloodGlucose",
    metric: "BLOOD_GLUCOSE",
  },
+  ketones: { labelKey: "insights.navBloodKetones", metric: "BLOOD_KETONES" },
  "skin-temperature": {
    labelKey: "insights.navSkinTemperature",
    metric: "SKIN_TEMPERATURE",
@@ -0,0 +1,109 @@
+"use client";
+
+import dynamic from "next/dynamic";
+import { Divide } from "lucide-react";
+
+import {
+  ChartErrorBoundary,
+  ChartErrorState,
+} from "@/components/charts/chart-error-state";
+import { ChartSkeleton } from "@/components/charts/chart-skeleton";
+import { TileHeader } from "@/components/insights/tile-header";
+import {
+  Card,
+  CardContent,
+  CardDescription,
+  CardHeader,
+} from "@/components/ui/card";
+import { EmptyState } from "@/components/ui/empty-state";
+import { useFormatters, useTranslations } from "@/lib/i18n/context";
+import { GKI_COMPONENT_UNIT } from "@/lib/measurements/glucose-ketone-index";
+import { useGlucoseKetoneIndexSeries } from "@/lib/queries/use-glucose-ketone-index";
+import { importWithRetry } from "@/lib/retry-import";
+
+// The line chart the custom metrics draw: a value over time with range tabs
+// and the day doors. Loaded through the one recharts boundary.
+const IndexChartLazy = dynamic(
+  () =>
+    importWithRetry(() => import("@/components/charts/chart-runtime")).then(
+      (mod) => ({ default: mod.CustomMetricChart }),
+    ),
+  { ssr: false, loading: () => <ChartSkeleton /> },
+);
+
+/**
+ * The glucose-ketone index (#1367), beneath the ketone chart. Every point is
+ * one ketone reading and the glucose reading the server paired with it; the
+ * value is the server's and is drawn as given. The latest pair is spelled out
+ * so the number can be traced to the two readings it came from. No band and
+ * no verdict: what the index should be is the treating clinician's call.
+ */
+export function GkiCard() {
+  const { t } = useTranslations();
+  const fmt = useFormatters();
+  const query = useGlucoseKetoneIndexSeries();
+  const points = query.data?.points ?? [];
+  const latest = points[points.length - 1];
+  const title = t("measurements.glucoseKetoneIndex");
+
+  return (
+    <Card data-slot="gki-card" aria-busy={query.isFetching || undefined}>
+      <CardHeader>
+        <TileHeader icon={Divide} title={title} titleAs="h2" />
+        <CardDescription>
+          {t("insights.bloodKetones.gki.description")}
+        </CardDescription>
+      </CardHeader>
+      <CardContent className="space-y-3">
+        {query.isPending ? (
+          <ChartSkeleton />
+        ) : query.isError ? (
+          <ChartErrorState
+            error={query.error}
+            title={t("charts.errorTitle")}
+            actionLabel={t("common.retry")}
+            actionContext={title}
+            onAction={() => void query.refetch()}
+          />
+        ) : !latest ? (
+          <EmptyState
+            variant="plain"
+            size="compact"
+            title={t("insights.bloodKetones.gki.emptyTitle")}
+            description={t("insights.bloodKetones.gki.emptyDescription")}
+          />
+        ) : (
+          <>
+            <p className="text-sm" data-slot="gki-latest">
+              {t("insights.bloodKetones.gki.latest", {
+                value: fmt.number(latest.value, 1),
+                glucose: fmt.number(latest.gki.glucoseMmol, 1),
+                ketones: fmt.number(latest.gki.ketonesMmol, 1),
+                unit: GKI_COMPONENT_UNIT,
+                date: fmt.dateTime(latest.at),
+              })}
+            </p>
+            <ChartErrorBoundary>
+              <IndexChartLazy
+                name={title}
+                unit=""
+                targetLow={null}
+                targetHigh={null}
+                decimals={1}
+                entries={points.map((p) => ({
+                  id: p.id,
+                  customMetricId: "",
+                  value: p.value,
+                  unit: "",
+                  measuredAt: p.at,
+                  note: null,
+                  createdAt: p.at,
+                }))}
+              />
+            </ChartErrorBoundary>
+          </>
+        )}
+      </CardContent>
+    </Card>
+  );
+}
@@ -0,0 +1,73 @@
+import { describe, expect, it } from "vitest";
+
+import { ketoneFingerstickBatch } from "@/components/measurements/ketone-fingerstick";
+import { createBatchMeasurementSchema } from "@/lib/validations/measurement";
+
+const AT = "2026-11-01T08:00:00.000Z";
+
+function batch(
+  overrides: Partial<Parameters<typeof ketoneFingerstickBatch>[0]>,
+) {
+  return ketoneFingerstickBatch({
+    ketones: "1.2",
+    glucose: "",
+    glucoseUnit: "mg/dL",
+    glucoseContext: "FASTING",
+    measuredAt: AT,
+    notes: "",
+    ...overrides,
+  });
+}
+
+describe("ketoneFingerstickBatch", () => {
+  it("posts the ketones alone when the meter gave no glucose", () => {
+    expect(batch({})).toEqual([
+      { type: "BLOOD_KETONES", value: 1.2, measuredAt: AT, notes: undefined },
+    ]);
+  });
+
+  it("posts the glucose and the ketones with one timestamp", () => {
+    const rows = batch({
+      glucose: "81",
+      ketones: "1,5",
+      notes: "after breakfast",
+    });
+    expect(rows).toEqual([
+      {
+        type: "BLOOD_GLUCOSE",
+        value: 81,
+        measuredAt: AT,
+        notes: "after breakfast",
+        glucoseContext: "FASTING",
+      },
+      {
+        type: "BLOOD_KETONES",
+        value: 1.5,
+        measuredAt: AT,
+        notes: "after breakfast",
+      },
+    ]);
+    // The batch the route validates: the shape the form sends is accepted.
+    expect(
+      createBatchMeasurementSchema.safeParse({ measurements: rows }).success,
+    ).toBe(true);
+  });
+
+  it("stores glucose typed in mmol/L as mg/dL", () => {
+    const rows = batch({ glucose: "4.5", glucoseUnit: "mmol/L" });
+    expect(rows?.[0]).toMatchObject({ type: "BLOOD_GLUCOSE", value: 81 });
+  });
+
+  it("refuses a number it cannot read rather than dropping half the pair", () => {
+    expect(batch({ ketones: "" })).toBeNull();
+    expect(batch({ ketones: "abc" })).toBeNull();
+    expect(batch({ glucose: "lots" })).toBeNull();
+  });
+
+  it("is refused by the route's schema above the meters' range", () => {
+    const rows = batch({ ketones: "12", glucose: "90" });
+    expect(
+      createBatchMeasurementSchema.safeParse({ measurements: rows }).success,
+    ).toBe(false);
+  });
+});
@@ -0,0 +1,56 @@
+/**
+ * One fingerstick as one entry (#1367): the ketones, and the glucose from the
+ * same drop when the meter gave one, as the batch the measurements route
+ * writes in one transaction. Both readings carry the one timestamp, so the
+ * server pairs them exactly when it derives the glucose-ketone index.
+ *
+ * Pure, so the form's write path can be pinned without rendering it.
+ */
+import { toCanonicalMgdl, type GlucoseUnit } from "@/lib/glucose";
+import { parseDecimalEntry } from "@/lib/measurements/entry-units";
+
+export interface FingerstickRow {
+  type: "BLOOD_GLUCOSE" | "BLOOD_KETONES";
+  value: number;
+  measuredAt: string;
+  notes?: string;
+  glucoseContext?: string;
+}
+
+/**
+ * The rows to post, glucose first, or null when a typed number does not read
+ * as one. An empty glucose field means the meter gave ketones only.
+ */
+export function ketoneFingerstickBatch(input: {
+  ketones: string;
+  glucose: string;
+  /** The unit the glucose was typed in: the account's glucose unit. */
+  glucoseUnit: GlucoseUnit;
+  glucoseContext: string;
+  measuredAt: string;
+  notes: string;
+}): FingerstickRow[] | null {
+  const ketones = parseDecimalEntry(input.ketones);
+  if (ketones === null) return null;
+  const notes = input.notes || undefined;
+  const ketoneRow: FingerstickRow = {
+    type: "BLOOD_KETONES",
+    value: ketones,
+    measuredAt: input.measuredAt,
+    notes,
+  };
+  if (input.glucose.trim() === "") return [ketoneRow];
+  const glucose = parseDecimalEntry(input.glucose);
+  if (glucose === null) return null;
+  return [
+    {
+      type: "BLOOD_GLUCOSE",
+      // Stored in mg/dL whatever the reader types in.
+      value: toCanonicalMgdl(glucose, input.glucoseUnit),
+      measuredAt: input.measuredAt,
+      notes,
+      glucoseContext: input.glucoseContext,
+    },
+    ketoneRow,
+  ];
+}
@@ -0,0 +1,127 @@
+"use client";
+
+import { Loader2, MoreHorizontal, Plus, RotateCcw } from "lucide-react";
+
+import { Button } from "@/components/ui/button";
+import {
+  DropdownMenu,
+  DropdownMenuContent,
+  DropdownMenuItem,
+  DropdownMenuTrigger,
+} from "@/components/ui/dropdown-menu";
+import { FieldGroup } from "@/components/ui/field-group";
+import { Input } from "@/components/ui/input";
+import { glucoseFractionDigits, type GlucoseUnit } from "@/lib/glucose";
+import { useTranslations } from "@/lib/i18n/context";
+
+/**
+ * The measurement form's action row: the reset menu, Cancel and Save. The
+ * Save button names the form by id, so it still submits it when the row is
+ * portalled into a sheet's footer slot.
+ */
+export function MeasurementFormFooter({
+  loading,
+  formId,
+  onReset,
+  onCancel,
+}: {
+  loading: boolean;
+  formId: string;
+  onReset: () => void;
+  onCancel?: () => void;
+}) {
+  const { t } = useTranslations();
+  return (
+    <div className="flex w-full items-center justify-between gap-2">
+      <DropdownMenu>
+        <DropdownMenuTrigger asChild>
+          <Button
+            type="button"
+            variant="outline"
+            size="icon"
+            className="size-11"
+            disabled={loading}
+            aria-label={t("common.moreOptions")}
+          >
+            <MoreHorizontal className="h-4 w-4" />
+          </Button>
+        </DropdownMenuTrigger>
+        <DropdownMenuContent align="start">
+          <DropdownMenuItem onClick={onReset}>
+            <RotateCcw className="mr-2 h-4 w-4" />
+            {t("measurements.formReset")}
+          </DropdownMenuItem>
+        </DropdownMenuContent>
+      </DropdownMenu>
+
+      <div className="flex items-center gap-2">
+        {onCancel && (
+          <Button
+            type="button"
+            variant="outline"
+            onClick={onCancel}
+            disabled={loading}
+          >
+            {t("common.cancel")}
+          </Button>
+        )}
+        <Button type="submit" form={formId} disabled={loading}>
+          {loading ? (
+            <Loader2 className="h-4 w-4 animate-spin motion-reduce:animate-none" />
+          ) : (
+            <Plus className="h-4 w-4" />
+          )}
+          {t("common.save")}
+        </Button>
+      </div>
+    </div>
+  );
+}
+
+/**
+ * #1367 — the glucose a ketone meter reads from the same drop, beside the
+ * ketones. Optional: a meter that reads ketones only leaves it empty. It asks
+ * in the account's glucose unit, which the write path converts back to mg/dL.
+ */
+export function PairedGlucoseField({
+  value,
+  onChange,
+  unit,
+  invalid,
+  describedBy,
+}: {
+  value: string;
+  onChange: (next: string) => void;
+  unit: GlucoseUnit;
+  invalid: boolean;
+  describedBy?: string;
+}) {
+  const { t } = useTranslations();
+  return (
+    <FieldGroup
+      htmlFor="paired-glucose"
+      label={
+        <>
+          {t("measurements.pairedGlucoseLabel", { unit })}
+          <span className="text-muted-foreground ml-1 font-normal">
+            ({t("common.optional")})
+          </span>
+        </>
+      }
+      hint={t("measurements.pairedGlucoseHint")}
+    >
+      <Input
+        id="paired-glucose"
+        // Not `type="number"`, like the value field: a decimal comma must
+        // survive on every engine.
+        inputMode="decimal"
+        enterKeyHint="next"
+        value={value}
+        onChange={(e) => onChange(e.target.value)}
+        placeholder={glucoseFractionDigits(unit) > 0 ? "5.3" : "95"}
+        aria-invalid={invalid || undefined}
+        aria-describedby={describedBy}
+      />
+    </FieldGroup>
+  );
+}
@@ -5,13 +5,6 @@ import { useActiveRecordName } from "@/hooks/use-record-capabilities";
 import { useId, useState } from "react";
 import { createPortal } from "react-dom";
 import { useQueryClient } from "@tanstack/react-query";
-import { Button } from "@/components/ui/button";
-import {
-  DropdownMenu,
-  DropdownMenuContent,
-  DropdownMenuItem,
-  DropdownMenuTrigger,
-} from "@/components/ui/dropdown-menu";
 import { Input } from "@/components/ui/input";
 import { DateTimeField } from "@/components/ui/date-time-field";
 import { FieldGroup } from "@/components/ui/field-group";
@@ -23,7 +16,6 @@ import {
  SelectTrigger,
  SelectValue,
 } from "@/components/ui/select";
-import { Loader2, MoreHorizontal, Plus, RotateCcw } from "lucide-react";
 import { toast } from "sonner";
 import { useTranslations } from "@/lib/i18n/context";
 import { useUnitDisplay } from "@/hooks/use-unit-display";
@@ -50,6 +42,11 @@ import {
 } from "@/lib/measurements/last-used-type";

 import { DurationReadAs } from "./duration-read-as";
+import { ketoneFingerstickBatch } from "./ketone-fingerstick";
+import {
+  MeasurementFormFooter,
+  PairedGlucoseField,
+} from "./measurement-form-parts";

 const MAX_COMMENT_LENGTH = MEASUREMENT_NOTES_MAX_LENGTH;

@@ -104,6 +101,13 @@ export const MEASUREMENT_TYPES = [
    unit: "mg/dL",
    placeholder: "95",
  },
+  // #1367 — ketones, with the same fingerstick's glucose (one entry).
+  {
+    value: "BLOOD_KETONES",
+    labelKey: "measurements.typeBloodKetones",
+    unit: "mmol/L",
+    placeholder: "1.2",
+  },
  {
    value: "TOTAL_BODY_WATER",
    labelKey: "measurements.typeTotalBodyWater",
@@ -360,6 +364,8 @@ export function MeasurementForm({
  const [sysBp, setSysBp] = useState("");
  const [diaBp, setDiaBp] = useState("");
  const [pulse, setPulse] = useState("");
+  // The glucose of a fingerstick entered with its ketones; optional.
+  const [pairedGlucose, setPairedGlucose] = useState("");
  const [notes, setNotes] = useState("");
  const [measuredAt, setMeasuredAt] = useState(() =>
    localDateTimeValue(defaultDate),
@@ -383,6 +389,7 @@ export function MeasurementForm({
  const typeInfo = MEASUREMENT_TYPES.find((t) => t.value === type);
  const isBpMode = type === "BLOOD_PRESSURE";
  const isGlucoseMode = type === "BLOOD_GLUCOSE";
+  const isKetoneMode = type === "BLOOD_KETONES";
  // A duration field (sleep, in hours) also reads "7:30" and "7h 30m"; the
  // hint under it says how the entry was understood.
  const durationUnit = durationEntryUnit(type);
@@ -395,6 +402,7 @@ export function MeasurementForm({
    setSysBp("");
    setDiaBp("");
    setPulse("");
+    setPairedGlucose("");
    setNotes("");
    setMeasuredAt(localDateTimeValue(defaultDate));
    setError(null);
@@ -440,6 +448,21 @@ export function MeasurementForm({
          });
        }

+        await apiPost("/api/measurements", batch);
+      } else if (isKetoneMode) {
+        // One fingerstick, posted as one transaction (`ketone-fingerstick.ts`).
+        const batch = ketoneFingerstickBatch({
+          ketones: value,
+          glucose: pairedGlucose,
+          glucoseUnit,
+          glucoseContext,
+          measuredAt: timestamp,
+          notes,
+        });
+        if (!batch) {
+          setError(t("measurements.saveError"));
+          return;
+        }
        await apiPost("/api/measurements", batch);
      } else {
        // Single measurement. Canonical storage stays SI: an imperial user
@@ -503,6 +526,7 @@ export function MeasurementForm({
      setSysBp("");
      setDiaBp("");
      setPulse("");
+      setPairedGlucose("");
      setNotes("");
      await invalidateKeys(queryClient, measurementDependentKeys);
      await refetchInactiveDailyReads(queryClient);
@@ -528,49 +552,12 @@ export function MeasurementForm({
  }

  const footerNode = (
-    <div className="flex w-full items-center justify-between gap-2">
-      <DropdownMenu>
-        <DropdownMenuTrigger asChild>
-          <Button
-            type="button"
-            variant="outline"
-            size="icon"
-            className="size-11"
-            disabled={loading}
-            aria-label={t("common.moreOptions")}
-          >
-            <MoreHorizontal className="h-4 w-4" />
-          </Button>
-        </DropdownMenuTrigger>
-        <DropdownMenuContent align="start">
-          <DropdownMenuItem onClick={resetForm}>
-            <RotateCcw className="mr-2 h-4 w-4" />
-            {t("measurements.formReset")}
-          </DropdownMenuItem>
-        </DropdownMenuContent>
-      </DropdownMenu>
-
-      <div className="flex items-center gap-2">
-        {onCancel && (
-          <Button
-            type="button"
-            variant="outline"
-            onClick={onCancel}
-            disabled={loading}
-          >
-            {t("common.cancel")}
-          </Button>
-        )}
-        <Button type="submit" form={formId} disabled={loading}>
-          {loading ? (
-            <Loader2 className="h-4 w-4 animate-spin motion-reduce:animate-none" />
-          ) : (
-            <Plus className="h-4 w-4" />
-          )}
-          {t("common.save")}
-        </Button>
-      </div>
-    </div>
+    <MeasurementFormFooter
+      loading={loading}
+      formId={formId}
+      onReset={resetForm}
+      onCancel={onCancel}
+    />
  );

  return (
@@ -718,7 +705,17 @@ export function MeasurementForm({
        </FieldGroup>
      )}

-      {isGlucoseMode && (
+      {isKetoneMode && (
+        <PairedGlucoseField
+          value={pairedGlucose}
+          onChange={setPairedGlucose}
+          unit={glucoseUnit}
+          invalid={!!error}
+          describedBy={errorDescriptor}
+        />
+      )}
+
+      {(isGlucoseMode || (isKetoneMode && pairedGlucose.trim() !== "")) && (
        <FieldGroup
          htmlFor="glucose-context"
          label={t("measurements.glucoseContext")}
@@ -48,6 +48,7 @@ export const MEASUREMENT_TYPE_LABEL_KEYS: Record<string, string> = {
  SLEEP_DURATION: "measurements.typeSleep",
  ACTIVITY_STEPS: "measurements.typeSteps",
  BLOOD_GLUCOSE: "measurements.typeBloodGlucose",
+  BLOOD_KETONES: "measurements.typeBloodKetones",
  TOTAL_BODY_WATER: "measurements.typeTotalBodyWater",
  BONE_MASS: "measurements.typeBoneMass",
  OXYGEN_SATURATION: "measurements.typeOxygenSaturation",
@@ -159,6 +160,7 @@ export const MEASUREMENT_TYPE_ICONS: Record<string, LucideIcon> = {
  SLEEP_DURATION: Moon,
  ACTIVITY_STEPS: Footprints,
  BLOOD_GLUCOSE: Droplet,
+  BLOOD_KETONES: Droplet,
  TOTAL_BODY_WATER: Droplet,
  BONE_MASS: Bone,
  OXYGEN_SATURATION: Wind,
@@ -13,6 +13,7 @@ export const MEASUREMENT_TYPE_COLORS: Record<string, string> = {
  SLEEP_DURATION: "bg-chart-2/10 text-chart-2 dark:bg-chart-2/20",
  ACTIVITY_STEPS: "bg-chart-2/10 text-chart-2 dark:bg-chart-2/20",
  BLOOD_GLUCOSE: "bg-chart-3/10 text-chart-3 dark:bg-chart-3/20",
+  BLOOD_KETONES: "bg-chart-3/10 text-chart-3 dark:bg-chart-3/20",
  TOTAL_BODY_WATER: "bg-chart-2/10 text-chart-2 dark:bg-chart-2/20",
  BONE_MASS: "bg-chart-4/10 text-chart-4 dark:bg-chart-4/20",
  OXYGEN_SATURATION: "bg-chart-5/10 text-chart-5 dark:bg-chart-5/20",
@@ -131,10 +131,12 @@ const EXPECTED_TYPES = [
  "ACUTE_TRAINING_LOAD",
  // ── resting energy (#1340) ──
  "BASAL_ENERGY_BURNED",
+  // ── blood ketones (#1367) ──
+  "BLOOD_KETONES",
 ] as const;

 describe("measurementTypeEnum coverage", () => {
-  it("exposes the 91 canonical measurement types", () => {
+  it("exposes the 92 canonical measurement types", () => {
    expect([...measurementTypeEnum.options].sort()).toEqual(
      [...EXPECTED_TYPES].sort(),
    );
@@ -341,6 +341,7 @@ export const CHART_OVERLAY_KEYS = [
  "scoreSleep",
  "scoreStress",
  "scoreStrain",
+  "bloodKetones", // #1367 — the chart on the ketones page.
 ] as const;
 export type ChartOverlayKey = (typeof CHART_OVERLAY_KEYS)[number];

@@ -29,6 +29,7 @@ import {
 import { DAY_SCORE_MEASUREMENT_TYPES, readDayScores } from "@/lib/day/scores";
 import { measurementTypeVisible, type DayAccess } from "@/lib/day/sections";
 import { readDayBands, shapeDayValues } from "@/lib/day/values";
+import { readGlucoseKetoneIndex } from "@/lib/measurements/read-glucose-ketone-index";
 import {
  resolveDayReadings,
  type DayReadings,
@@ -153,6 +154,19 @@ export async function loadDay(args: LoadDayArgs): Promise<DayResponse> {
  ]);

  const presentTypes = [...readings.rowsByType.keys()];
+  // The index reveals the glucose it was built from, so it needs both
+  // reading types visible, not only the ketones the day holds.
+  const gkiReadable =
+    readings.rowsByType.has("BLOOD_KETONES") &&
+    typeVisible("BLOOD_KETONES") &&
+    typeVisible("BLOOD_GLUCOSE");
+  const glucoseKetoneIndex = gkiReadable
+    ? await readGlucoseKetoneIndex({
+        userId: recordId,
+        from: dayStart,
+        to: dayEnd,
+      })
+    : [];
  const [bands, notable] =
    presentTypes.length === 0
      ? [new Map(), []]
@@ -194,6 +208,7 @@ export async function loadDay(args: LoadDayArgs): Promise<DayResponse> {
    counts: { values: values.length, entries: events.length },
    running,
    values,
+    ...(glucoseKetoneIndex.length > 0 ? { glucoseKetoneIndex } : {}),
    events,
    notable: notable.map(({ kind, type, params }) => ({ kind, type, params })),
    scores,
@@ -117,6 +117,24 @@ const dayValue = z
  })
  .meta({ id: "DayValue" });

+/**
+ * #1367 — one glucose-ketone index of the day, derived from a ketone reading
+ * and the glucose reading paired with it; never stored.
+ */
+const dayGlucoseKetoneIndex = z
+  .object({
+    at: instant.describe("The ketone reading's instant."),
+    value: z.number().describe("The index, to one decimal."),
+    ketoneId: z.string().describe("The ketone reading's id."),
+    glucoseId: z.string().describe("The paired glucose reading's id."),
+    glucoseAt: instant.describe("The paired glucose reading's instant."),
+    ketonesMmol: z.number().describe("Beta-hydroxybutyrate, mmol/L."),
+    glucoseMmol: z
+      .number()
+      .describe("The paired glucose in mmol/L, one decimal."),
+  })
+  .meta({ id: "DayGlucoseKetoneIndex" });
+
 const dayEvent = z
  .object({
    at: instant
@@ -232,6 +250,12 @@ export const dayResponseSchema = z
    }),
    running: z.array(dayRunningItem),
    values: z.array(dayValue),
+    glucoseKetoneIndex: z
+      .array(dayGlucoseKetoneIndex)
+      .optional()
+      .describe(
+        "#1367 — the day's glucose-ketone index, oldest first: glucose (mmol/L) over ketones (mmol/L) for each ketone reading above zero with a glucose reading at the same instant or within 15 minutes either side. Computed at read time; show it as given. Absent when the day has none, when either reading type is hidden from the caller, and on older servers.",
+      ),
    events: z.array(dayEvent),
    notable: z.array(dayNotable),
    scores: z
@@ -186,8 +186,9 @@ function groupSubHeadRow(label: string): VitalTableRow {
 }

 /**
- * Per-context glucose rows. Values are stored canonically in mg/dL and print
- * in the owner's unit, in the precision their readings carry.
+ * The glucose group's own rows: one per meal context, stored canonically in
+ * mg/dL and printed in the owner's unit in the precision their readings
+ * carry, then the glucose-ketone index (#1367), a ratio without a unit.
 */
 function glucoseContextTableRows(
  context: DoctorReportPdfRenderContext,
@@ -209,6 +210,17 @@ function glucoseContextTableRows(
      String(s.count),
    ]);
  }
+  const gki = data.glucoseKetoneIndex;
+  if (gki) {
+    rows.push([
+      t("measurements.glucoseKetoneIndex"),
+      num(gki.latest, 1),
+      num(gki.avg, 1),
+      num(gki.min, 1),
+      num(gki.max, 1),
+      String(gki.count),
+    ]);
+  }
  return rows;
 }

@@ -118,6 +118,13 @@ export interface DoctorReportData {
   * `stillLearning` when the period is too thin to assert clinically.
   */
  glucoseClinical: GlucoseClinicalMetrics;
+  /**
+   * #1367 — the glucose-ketone index over the period (count, mean, range,
+   * latest), derived at read time from each ketone reading and the glucose
+   * reading paired with it. Null when there is none or when either reading
+   * type is withheld. Optional so older fixtures still typecheck.
+   */
+  glucoseKetoneIndex?: DoctorReportStats | null;
  bmi: number | null;
  /** Keyed by medication id; see `DoctorReportCompliance`. */
  compliance: Record<string, DoctorReportCompliance>;
@@ -67,6 +67,7 @@ import {
 import { loadDenseMeasurementBuckets } from "./dense-buckets";
 import { summariseDenseBuckets } from "./measurement-series";
 import { emptyGlucoseClinical } from "./glucose-panel";
+import { readReportGki } from "./glucose-ketone-index";
 import { buildAdministrationLedger, buildGlp1Block } from "./medications";
 import { loadReportWorkouts } from "./workouts";
 import { loadReportMedicationEffects } from "./medication-effects";
@@ -249,9 +250,8 @@ export async function collectDoctorReportData(
          ...(rawExcluded.length > 0 ? { type: { notIn: rawExcluded } } : {}),
        },
        orderBy: { measuredAt: "asc" },
-        // Narrow select: the collector reads exactly these seven fields.
-        // The full-width read pulled every column — including the encrypted
-        // notes — across up to 730 days of rows.
+        // Narrow select: the full-width read pulled every column, encrypted
+        // notes included, across up to 730 days of rows.
        select: {
          type: true,
          value: true,
@@ -739,6 +739,7 @@ export async function collectDoctorReportData(
    glucoseStats,
    glucoseRanges,
    glucoseClinical,
+    glucoseKetoneIndex: await readReportGki(gate, stats, userId, start, end),
    glucoseUnit: resolveGlucoseUnit(userProfile?.glucoseUnit ?? null),
    bmi: gate.admits("BODY_MASS_INDEX") ? bmi : null,
    compliance: gate.admits("MEDICATION_COMPLIANCE") ? compliance : {},
@@ -0,0 +1,45 @@
+/**
+ * The glucose-ketone index in the doctor report (#1367): count, mean, range
+ * and latest over the report window, read by the one pairing rule
+ * (`read-glucose-ketone-index.ts`) so the report carries the numbers the
+ * ketones page shows.
+ *
+ * Both leaves must admit it. The index is glucose over ketones, so beside the
+ * ketone series it gives the glucose back exactly: a report that withholds
+ * glucose withholds the index too.
+ */
+import type { DoctorReportStats } from "@/lib/doctor-report-types";
+import { summariseGlucoseKetoneIndex } from "@/lib/measurements/glucose-ketone-index";
+import { readGlucoseKetoneIndex } from "@/lib/measurements/read-glucose-ketone-index";
+
+import type { ReportGate } from "./selection-gate";
+
+export async function readReportGki(
+  gate: ReportGate,
+  /** The report's own stats: no ketone row in the window, no read. */
+  stats: Readonly<Record<string, DoctorReportStats>>,
+  userId: string,
+  /** The report window; `end` is inclusive, as the measurement read has it. */
+  start: Date,
+  end: Date,
+): Promise<DoctorReportStats | null> {
+  if (!gate.admits("BLOOD_KETONES") || !gate.admits("BLOOD_GLUCOSE")) {
+    return null;
+  }
+  if (!stats.BLOOD_KETONES?.count) return null;
+  const points = await readGlucoseKetoneIndex({
+    userId,
+    from: start,
+    to: new Date(end.getTime() + 1),
+  });
+  const summary = summariseGlucoseKetoneIndex(points);
+  if (!summary) return null;
+  return {
+    avg: summary.mean,
+    min: summary.min,
+    max: summary.max,
+    count: summary.count,
+    latest: summary.latest,
+    latestAt: points[points.length - 1]!.at,
+  };
+}
@@ -196,6 +196,32 @@ describe("measurementSeriesObservation", () => {
    expect(o.code.coding?.[0]?.code).toBe(MEASUREMENT_LOINC.WEIGHT.loinc);
  });

+  it("codes blood ketones as beta-hydroxybutyrate in blood (#1367)", () => {
+    const o = measurementSeriesObservation(
+      {
+        id: "k1",
+        type: "BLOOD_KETONES",
+        value: 1.4,
+        valueMin: null,
+        valueMax: null,
+        measuredAt: AT,
+        glucoseContext: null,
+      },
+      "mg/dL",
+      null,
+    )!;
+    assertR4Observation(o);
+    expect(o.category?.[0]?.coding?.[0]?.code).toBe("laboratory");
+    expect(o.code.coding).toEqual([
+      {
+        system: "http://loinc.org",
+        code: "104816-4",
+        display: "Beta hydroxybutyrate [Moles/volume] in Blood",
+      },
+    ]);
+    expect(o.valueQuantity).toMatchObject({ value: 1.4, unit: "mmol/L" });
+  });
+
  it("labels RMSSD as its own text-only statistic, never under SDNN's code", () => {
    const o = measurementSeriesObservation(
      {
@@ -29,6 +29,7 @@ export const ALLOWED_CHART_TOKENS = [
  "metric:SLEEP_DURATION",
  "metric:ACTIVITY_STEPS",
  "metric:BLOOD_GLUCOSE",
+  "metric:BLOOD_KETONES",
  "metric:TOTAL_BODY_WATER",
  "metric:BONE_MASS",
  "metric:OXYGEN_SATURATION",
@@ -80,6 +80,8 @@ export type InsightMetric =
  // `summaries[metric].count > 0` with no new handler branch (the
  // metric auto-lights-up the moment the first reading lands).
  | "BLOOD_GLUCOSE"
+  // #1367 — blood ketones, keyed on its MeasurementType like glucose.
+  | "BLOOD_KETONES"
  | "TOTAL_BODY_WATER"
  | "BONE_MASS"
  // Body fat percentage, keyed on its MeasurementType like the rest of the
@@ -139,6 +139,8 @@ const SUB_PAGE_METRIC = {
  daylight: ["TIME_IN_DAYLIGHT"],
  // ── metabolic (v1.7.0) ──
  "blood-glucose": ["BLOOD_GLUCOSE"],
+  // #1367 — blood ketones, with the glucose-ketone index beneath the chart.
+  ketones: ["BLOOD_KETONES"],
  "skin-temperature": ["SKIN_TEMPERATURE"],
  // v1.10.0 — overnight wrist temperature joins the metabolic cluster.
  "wrist-temperature": ["WRIST_TEMPERATURE"],
@@ -243,6 +245,7 @@ export const SUB_PAGE_GROUP: Partial<Record<SubPageSlug, SubPageGroup>> = {
  daylight: "environment",
  // metabolic (v1.7.0)
  "blood-glucose": "metabolic",
+  ketones: "metabolic",
  "skin-temperature": "metabolic",
  // ── v1.10.0 — additive HealthKit signals (WX-A) ──
  // activity / mobility cluster
@@ -105,6 +105,9 @@ const MEASUREMENT_TYPES_WITHOUT_HK_COUNTERPART = new Set<MeasurementType>([
  // derivation as PHQ-9 / GAD-7. No HK mapping by design.
  "WHO5_SCORE",
  "SCI_SCORE",
+  // Blood ketones (#1367): HealthKit has no beta-hydroxybutyrate quantity
+  // type, so a ketone reading is typed by hand. No HK mapping by design.
+  "BLOOD_KETONES",
 ]);

 describe("APPLE_HEALTH_TYPE_MAP", () => {
@@ -0,0 +1,156 @@
+import { describe, expect, it } from "vitest";
+
+import { MGDL_PER_MMOL } from "@/lib/glucose";
+import {
+  GKI_PAIRING_WINDOW_MINUTES,
+  glucoseKetoneIndex,
+  pairGlucoseKetoneIndex,
+  summariseGlucoseKetoneIndex,
+  type GkiReading,
+} from "@/lib/measurements/glucose-ketone-index";
+
+const T0 = Date.parse("2026-11-01T08:00:00.000Z");
+const MIN = 60_000;
+
+function reading(
+  id: string,
+  offsetMin: number,
+  value: number,
+  source = "MANUAL",
+): GkiReading {
+  return { id, measuredAt: new Date(T0 + offsetMin * MIN), value, source };
+}
+
+describe("glucoseKetoneIndex", () => {
+  it("divides glucose in mmol/L by ketones, converting with the one factor", () => {
+    // 90 mg/dL = 4.995 mmol/L; over 1.5 mmol/L ketones.
+    expect(glucoseKetoneIndex(90, 1.5)).toBeCloseTo(90 / MGDL_PER_MMOL / 1.5);
+    expect(glucoseKetoneIndex(90, 1.5)).toBeCloseTo(3.33, 2);
+  });
+
+  it("has no index without ketones or with a value that is not positive", () => {
+    expect(glucoseKetoneIndex(90, 0)).toBeNull();
+    expect(glucoseKetoneIndex(90, -1)).toBeNull();
+    expect(glucoseKetoneIndex(0, 1)).toBeNull();
+    expect(glucoseKetoneIndex(Number.NaN, 1)).toBeNull();
+    expect(glucoseKetoneIndex(90, Number.POSITIVE_INFINITY)).toBeNull();
+  });
+});
+
+describe("pairGlucoseKetoneIndex", () => {
+  it("pairs a fingerstick written with one timestamp", () => {
+    const [point, ...rest] = pairGlucoseKetoneIndex(
+      [reading("k1", 0, 1.2)],
+      [reading("g1", 0, 81)],
+    );
+    expect(rest).toEqual([]);
+    expect(point).toEqual({
+      ketoneId: "k1",
+      glucoseId: "g1",
+      at: new Date(T0).toISOString(),
+      glucoseAt: new Date(T0).toISOString(),
+      // 81 / 18.0182 = 4.4954 mmol/L; / 1.2 = 3.746 -> 3.7
+      value: 3.7,
+      ketonesMmol: 1.2,
+      glucoseMmol: 4.5,
+    });
+  });
+
+  it("prefers the same instant over a nearer-looking neighbour", () => {
+    const [point] = pairGlucoseKetoneIndex(
+      [reading("k1", 0, 1)],
+      [reading("g-early", -1, 200), reading("g-same", 0, 90)],
+    );
+    expect(point?.glucoseId).toBe("g-same");
+  });
+
+  it("takes the nearest glucose inside the window, before or after", () => {
+    const [before] = pairGlucoseKetoneIndex(
+      [reading("k1", 0, 1)],
+      [reading("g-far", -14, 100), reading("g-near", -3, 90)],
+    );
+    expect(before?.glucoseId).toBe("g-near");
+    const [after] = pairGlucoseKetoneIndex(
+      [reading("k1", 0, 1)],
+      [reading("g-after", 4, 90), reading("g-before", -9, 100)],
+    );
+    expect(after?.glucoseId).toBe("g-after");
+  });
+
+  it("pairs at the window's edge and never beyond it", () => {
+    const edge = GKI_PAIRING_WINDOW_MINUTES;
+    expect(
+      pairGlucoseKetoneIndex([reading("k1", 0, 1)], [reading("g1", edge, 90)]),
+    ).toHaveLength(1);
+    expect(
+      pairGlucoseKetoneIndex([reading("k1", 0, 1)], [reading("g1", -edge, 90)]),
+    ).toHaveLength(1);
+    expect(
+      pairGlucoseKetoneIndex(
+        [reading("k1", 0, 1)],
+        [reading("g1", edge + 0.5, 90), reading("g2", -(edge + 1), 90)],
+      ),
+    ).toEqual([]);
+  });
+
+  it("leaves out a ketone reading of zero or without a partner", () => {
+    expect(
+      pairGlucoseKetoneIndex(
+        [reading("k-zero", 0, 0), reading("k-alone", 120, 1.4)],
+        [reading("g1", 0, 90)],
+      ),
+    ).toEqual([]);
+  });
+
+  it("breaks a tie by source, then by the earlier reading", () => {
+    const [bySource] = pairGlucoseKetoneIndex(
+      [reading("k1", 0, 1, "MANUAL")],
+      [reading("g-cgm", 0, 140, "APPLE_HEALTH"), reading("g-own", 0, 90)],
+    );
+    expect(bySource?.glucoseId).toBe("g-own");
+    const [byTime] = pairGlucoseKetoneIndex(
+      [reading("k1", 0, 1)],
+      [reading("g-later", 5, 100), reading("g-earlier", -5, 90)],
+    );
+    expect(byTime?.glucoseId).toBe("g-earlier");
+  });
+
+  it("answers in ketone order whatever order the readings came in", () => {
+    const points = pairGlucoseKetoneIndex(
+      [reading("k2", 60, 2), reading("k1", 0, 1)],
+      [reading("g2", 61, 90), reading("g1", 1, 90)],
+    );
+    expect(points.map((p) => [p.ketoneId, p.glucoseId])).toEqual([
+      ["k1", "g1"],
+      ["k2", "g2"],
+    ]);
+  });
+
+  it("lets one glucose reading serve two ketone readings and names it", () => {
+    const points = pairGlucoseKetoneIndex(
+      [reading("k1", 0, 1), reading("k2", 6, 2)],
+      [reading("g1", 3, 90)],
+    );
+    expect(points.map((p) => p.glucoseId)).toEqual(["g1", "g1"]);
+    expect(points[1]!.value).toBeLessThan(points[0]!.value);
+  });
+});
+
+describe("summariseGlucoseKetoneIndex", () => {
+  it("summarises the indices and is null for none", () => {
+    expect(summariseGlucoseKetoneIndex([])).toBeNull();
+    const points = pairGlucoseKetoneIndex(
+      [reading("k1", 0, 1), reading("k2", 60, 2), reading("k3", 120, 4)],
+      [reading("g1", 0, 90), reading("g2", 60, 90), reading("g3", 120, 90)],
+    );
+    // 90 mg/dL = 4.995 mmol/L: indices 5.0, 2.5, 1.2.
+    expect(points.map((p) => p.value)).toEqual([5, 2.5, 1.2]);
+    expect(summariseGlucoseKetoneIndex(points)).toEqual({
+      count: 3,
+      mean: 2.9,
+      min: 1.2,
+      max: 5,
+      latest: 1.2,
+    });
+  });
+});
@@ -128,6 +128,7 @@ export const MEASUREMENT_CATEGORIES: ReadonlyMap<

  // ── Metabolic ──
  ["BLOOD_GLUCOSE", "metabolic"],
+  ["BLOOD_KETONES", "metabolic"],
  ["SKIN_TEMPERATURE", "metabolic"],
  // v1.10.0 — wrist temperature is an overnight skin-side reading;
  // it sits with skin temperature in the metabolic cluster.
@@ -0,0 +1,189 @@
+/**
+ * The glucose-ketone index (GKI), derived from a ketone reading and the
+ * glucose reading taken with it (#1367).
+ *
+ *   GKI = glucose (mmol/L) / beta-hydroxybutyrate (mmol/L)
+ *
+ * Glucose is stored in mg/dL and converted with {@link MGDL_PER_MMOL}, the one
+ * factor the tree uses for that conversion, so the glucose a GKI is built from
+ * is the same number every glucose surface shows. The index is computed when
+ * it is read and never stored: a stored ratio drifts the moment either reading
+ * it came from is edited or deleted, which is the failure a hand-typed GKI has.
+ *
+ * Pairing, per ketone reading:
+ *
+ *   1. A glucose reading at the same instant wins. A fingerstick entry writes
+ *      both readings with one timestamp, so this is the usual case.
+ *   2. Otherwise the nearest glucose reading no more than
+ *      {@link GKI_PAIRING_WINDOW_MINUTES} minutes before or after it.
+ *   3. Nothing further away. A ketone reading with no glucose inside the
+ *      window, or with a value of zero, has no index.
+ *
+ * Ties at the same distance go to the reading from the same source as the
+ * ketone reading (a manual fingerstick pairs with the manual glucose rather
+ * than with a sensor reading at the same minute), then to the earlier one. One
+ * glucose reading may serve two ketone readings taken close together; each
+ * index names the glucose reading it was built from.
+ *
+ * The figure is descriptive. Nothing here grades it: what a GKI should be is a
+ * matter for the plan a clinician sets.
+ */
+import { MGDL_PER_MMOL } from "@/lib/glucose";
+
+/**
+ * The widest gap between a ketone and a glucose reading that still pairs.
+ *
+ * Fifteen minutes covers two strips taken one after the other, a meter that
+ * reads ketones from a second drop, a reading typed in a few minutes late, and
+ * a sensor that samples every five minutes, while staying short enough that
+ * glucose has not moved on: after a meal it can rise by a few mg/dL a minute,
+ * so an hour-old reading describes a different moment and the ratio built from
+ * it would describe neither.
+ */
+export const GKI_PAIRING_WINDOW_MINUTES = 15;
+
+/**
+ * The unit both components of the index are in. Fixed, not the reader's
+ * glucose unit: the index is defined on mmol/L, and a ratio taken over mg/dL
+ * would be eighteen times larger and mean something else.
+ */
+export const GKI_COMPONENT_UNIT = "mmol/L";
+export const GKI_PAIRING_WINDOW_MS = GKI_PAIRING_WINDOW_MINUTES * 60_000;
+
+/** One stored reading, as the pairing needs it. */
+export interface GkiReading {
+  id: string;
+  measuredAt: Date;
+  /** Ketones in mmol/L; glucose in canonical mg/dL. */
+  value: number;
+  source: string;
+}
+
+/** One derived index, with the two readings it was built from. */
+export interface GlucoseKetoneIndexPoint {
+  /** The ketone reading's id. The index belongs to the ketone reading. */
+  ketoneId: string;
+  /** The glucose reading it was paired with. */
+  glucoseId: string;
+  /** The ketone reading's instant, ISO 8601. */
+  at: string;
+  /** The glucose reading's instant, ISO 8601. */
+  glucoseAt: string;
+  /** The index, to one decimal. */
+  value: number;
+  /** Beta-hydroxybutyrate as recorded, mmol/L. */
+  ketonesMmol: number;
+  /** The paired glucose in mmol/L, to one decimal. */
+  glucoseMmol: number;
+}
+
+/**
+ * The index of one glucose (mg/dL) and one ketone (mmol/L) value, unrounded,
+ * or null when it is undefined: no ketones, or a value that is not a positive
+ * finite number on either side.
+ */
+export function glucoseKetoneIndex(
+  glucoseMgdl: number,
+  ketonesMmol: number,
+): number | null {
+  if (!Number.isFinite(glucoseMgdl) || !Number.isFinite(ketonesMmol)) {
+    return null;
+  }
+  if (ketonesMmol <= 0 || glucoseMgdl <= 0) return null;
+  return glucoseMgdl / MGDL_PER_MMOL / ketonesMmol;
+}
+
+function oneDecimal(value: number): number {
+  return Math.round(value * 10) / 10;
+}
+
+/**
+ * Pair every ketone reading with its glucose reading and compute the index.
+ * Pure. Both lists may come in any order; the answer is in ketone-reading
+ * order (oldest first). Ketone readings without a partner are left out.
+ */
+export function pairGlucoseKetoneIndex(
+  ketones: readonly GkiReading[],
+  glucose: readonly GkiReading[],
+): GlucoseKetoneIndexPoint[] {
+  const sortedGlucose = [...glucose].sort(
+    (a, b) => a.measuredAt.getTime() - b.measuredAt.getTime(),
+  );
+  const sortedKetones = [...ketones].sort(
+    (a, b) =>
+      a.measuredAt.getTime() - b.measuredAt.getTime() ||
+      a.id.localeCompare(b.id),
+  );
+  const out: GlucoseKetoneIndexPoint[] = [];
+  let lo = 0;
+  for (const ketone of sortedKetones) {
+    if (!(ketone.value > 0)) continue;
+    const at = ketone.measuredAt.getTime();
+    // Ketone readings are walked in time order, so the window's lower edge
+    // only ever moves forward.
+    while (
+      lo < sortedGlucose.length &&
+      sortedGlucose[lo]!.measuredAt.getTime() < at - GKI_PAIRING_WINDOW_MS
+    ) {
+      lo++;
+    }
+    let best: GkiReading | null = null;
+    let bestRank: [number, number, number] | null = null;
+    for (let i = lo; i < sortedGlucose.length; i++) {
+      const candidate = sortedGlucose[i]!;
+      const t = candidate.measuredAt.getTime();
+      if (t > at + GKI_PAIRING_WINDOW_MS) break;
+      const rank: [number, number, number] = [
+        Math.abs(t - at),
+        candidate.source === ketone.source ? 0 : 1,
+        t,
+      ];
+      if (
+        bestRank === null ||
+        rank[0] < bestRank[0] ||
+        (rank[0] === bestRank[0] &&
+          (rank[1] < bestRank[1] ||
+            (rank[1] === bestRank[1] && rank[2] < bestRank[2])))
+      ) {
+        best = candidate;
+        bestRank = rank;
+      }
+    }
+    if (best === null) continue;
+    const index = glucoseKetoneIndex(best.value, ketone.value);
+    if (index === null) continue;
+    out.push({
+      ketoneId: ketone.id,
+      glucoseId: best.id,
+      at: ketone.measuredAt.toISOString(),
+      glucoseAt: best.measuredAt.toISOString(),
+      value: oneDecimal(index),
+      ketonesMmol: ketone.value,
+      glucoseMmol: oneDecimal(best.value / MGDL_PER_MMOL),
+    });
+  }
+  return out;
+}
+
+/** Count, mean, min, max and latest of a run of indices, or null when empty. */
+export interface GlucoseKetoneIndexSummary {
+  count: number;
+  mean: number;
+  min: number;
+  max: number;
+  latest: number;
+}
+
+export function summariseGlucoseKetoneIndex(
+  points: readonly GlucoseKetoneIndexPoint[],
+): GlucoseKetoneIndexSummary | null {
+  if (points.length === 0) return null;
+  const values = points.map((p) => p.value);
+  return {
+    count: values.length,
+    mean: oneDecimal(values.reduce((a, b) => a + b, 0) / values.length),
+    min: Math.min(...values),
+    max: Math.max(...values),
+    latest: values[values.length - 1]!,
+  };
+}
@@ -0,0 +1,86 @@
+/**
+ * Read the glucose-ketone index of a window (#1367): the ketone readings in
+ * it and the glucose readings within pairing reach of one, paired by
+ * `pairGlucoseKetoneIndex`. Every surface that shows the index (the series
+ * route, the day, the doctor report) reads it here, so the pairing rule has
+ * one implementation.
+ *
+ * Glucose and ketones carry no source ladder (neither is in `RANKED_TYPES`),
+ * so every live row of every source is a candidate, as on the glucose chart.
+ * The glucose read is bounded by the ketone readings: only rows within the
+ * pairing window of one are fetched, so a sensor writing every five minutes
+ * contributes a handful of rows per fingerstick, not the window's thousands.
+ */
+import { prisma } from "@/lib/db";
+
+import {
+  GKI_PAIRING_WINDOW_MINUTES,
+  GKI_PAIRING_WINDOW_MS,
+  pairGlucoseKetoneIndex,
+  type GkiReading,
+  type GlucoseKetoneIndexPoint,
+} from "./glucose-ketone-index";
+
+interface Row {
+  id: string;
+  value: number;
+  measured_at: Date;
+  source: string;
+}
+
+function toReading(row: Row): GkiReading {
+  return {
+    id: row.id,
+    value: row.value,
+    measuredAt: row.measured_at,
+    source: row.source,
+  };
+}
+
+/**
+ * The indices of the ketone readings taken in `[from, to)`, oldest first.
+ * A glucose reading just outside the window still pairs with a ketone reading
+ * just inside it.
+ */
+export async function readGlucoseKetoneIndex(args: {
+  userId: string;
+  from: Date;
+  to: Date;
+}): Promise<GlucoseKetoneIndexPoint[]> {
+  const { userId, from, to } = args;
+  const ketones = await prisma.$queryRaw<Row[]>`
+    SELECT k."id", k."value", k."measured_at", k."source"::text AS "source"
+    FROM measurements k
+    WHERE k."user_id" = ${userId}
+      AND k."type" = 'BLOOD_KETONES'::"measurement_type"
+      AND k."deleted_at" IS NULL
+      AND k."measured_at" >= ${from}
+      AND k."measured_at" < ${to}
+      AND k."value" > 0
+    ORDER BY k."measured_at" ASC, k."id" ASC
+  `;
+  if (ketones.length === 0) return [];
+  // An interval between two stored instants: no zone enters the arithmetic.
+  const reach = `${GKI_PAIRING_WINDOW_MINUTES} minutes`;
+  const glucose = await prisma.$queryRaw<Row[]>`
+    SELECT g."id", g."value", g."measured_at", g."source"::text AS "source"
+    FROM measurements g
+    WHERE g."user_id" = ${userId}
+      AND g."type" = 'BLOOD_GLUCOSE'::"measurement_type"
+      AND g."deleted_at" IS NULL
+      AND g."measured_at" >= ${new Date(from.getTime() - GKI_PAIRING_WINDOW_MS)}
+      AND g."measured_at" <= ${new Date(to.getTime() + GKI_PAIRING_WINDOW_MS)}
+      AND EXISTS (
+        SELECT 1 FROM measurements k
+        WHERE k."user_id" = ${userId}
+          AND k."type" = 'BLOOD_KETONES'::"measurement_type"
+          AND k."deleted_at" IS NULL
+          AND k."measured_at" >= ${from}
+          AND k."measured_at" < ${to}
+          AND k."value" > 0
+          AND k."measured_at" BETWEEN g."measured_at" - ${reach}::interval
+                                  AND g."measured_at" + ${reach}::interval
+      )
+  `;
+  return pairGlucoseKetoneIndex(ketones.map(toReading), glucose.map(toReading));
+}
@@ -44,7 +44,9 @@ export type SeriesKind =
  | "oxygenSaturation"
  | "restingHeartRate"
  | "heartRateVariability"
-  | "vo2Max";
+  | "vo2Max"
+  | "ketones"
+  | "glucoseKetoneIndex";

 export interface SeriesReferenceLine {
  value: number;
@@ -72,6 +72,10 @@ export const kindEnum = z.enum([
  "restingHeartRate",
  "heartRateVariability",
  "vo2Max",
+  // #1367 — blood ketones, and the glucose-ketone index derived from them and
+  // the glucose reading taken with each (`glucose-ketone-index.ts`).
+  "ketones",
+  "glucoseKetoneIndex",
 ]);

 export type SeriesKind = z.infer<typeof kindEnum>;
@@ -90,6 +94,11 @@ export const KIND_TO_TYPE: Record<SeriesKind, MeasurementType> = {
  restingHeartRate: "RESTING_HEART_RATE",
  heartRateVariability: "HEART_RATE_VARIABILITY",
  vo2Max: "VO2_MAX",
+  ketones: "BLOOD_KETONES",
+  // The index has no stored type. It belongs to its ketone reading, so the
+  // change direction and day values read as the ketone series' would; neither
+  // has a band, so nothing is judged.
+  glucoseKetoneIndex: "BLOOD_KETONES",
 };

 /**
@@ -119,6 +128,9 @@ export const SERIES_UNIT: Record<SeriesKind, string> = {
  restingHeartRate: "bpm",
  heartRateVariability: "ms",
  vo2Max: "mL/(kg·min)",
+  ketones: "mmol/L",
+  // A ratio of two concentrations in the same unit: dimensionless.
+  glucoseKetoneIndex: "ratio",
 };

 export interface SeriesPoint {
@@ -142,6 +154,17 @@ export interface SeriesPoint {
   */
  valueMin?: number | null;
  valueMax?: number | null;
+  /**
+   * #1367 — the two readings a `kind=glucoseKetoneIndex` point was built
+   * from. Absent for every other kind. `id` and `at` are the ketone
+   * reading's; this names the glucose reading paired with it.
+   */
+  gki?: {
+    glucoseId: string;
+    glucoseAt: string;
+    glucoseMmol: number;
+    ketonesMmol: number;
+  };
 }

 export function stdDev(values: number[]): number {
@@ -0,0 +1,37 @@
+/**
+ * `kind=glucoseKetoneIndex`: one point per ketone reading that pairs with a
+ * glucose reading (#1367). The index is derived at read time by the one
+ * pairing rule (`read-glucose-ketone-index.ts`); a client draws the value it
+ * is given and never recomputes it. Ketone readings are a few a day at most,
+ * so the window is never bucketed.
+ */
+import { readGlucoseKetoneIndex } from "@/lib/measurements/read-glucose-ketone-index";
+
+import type { SeriesRead } from "./kinds";
+
+export async function readGlucoseKetoneIndexSeries(
+  userId: string,
+  since: Date,
+): Promise<SeriesRead> {
+  const points = await readGlucoseKetoneIndex({
+    userId,
+    from: since,
+    // Open-ended: a reading stamped a moment ahead of the server clock is
+    // still the latest one.
+    to: new Date(Date.now() + 86_400_000),
+  });
+  return {
+    points: points.map((p) => ({
+      id: p.ketoneId,
+      at: p.at,
+      value: p.value,
+      secondary: null,
+      gki: {
+        glucoseId: p.glucoseId,
+        glucoseAt: p.glucoseAt,
+        glucoseMmol: p.glucoseMmol,
+        ketonesMmol: p.ketonesMmol,
+      },
+    })),
+  };
+}
@@ -28,6 +28,7 @@ import {
 } from "./kinds";
 import { readBloodPressureSeries } from "./read-blood-pressure";
 import { readBucketedSeries, takesBucketedRead } from "./read-bucketed";
+import { readGlucoseKetoneIndexSeries } from "./read-glucose-ketone-index";
 import { readRawSeries } from "./read-raw";
 import { readSleepSeries } from "./read-sleep";

@@ -40,6 +41,9 @@ async function readPoints(
 ): Promise<SeriesRead> {
  if (kind === "sleep") return readSleepSeries(userId, since, days);
  if (kind === "bloodPressure") return readBloodPressureSeries(userId, since);
+  if (kind === "glucoseKetoneIndex") {
+    return readGlucoseKetoneIndexSeries(userId, since);
+  }
  if (await takesBucketedRead(userId, kind, days, since)) {
    return readBucketedSeries(userId, kind, days, since);
  }
@@ -22,6 +22,7 @@ export const MEASUREMENT_TYPE_LABEL_KEYS: Record<MeasurementType, string> = {
  SLEEP_DURATION: "measurements.typeSleep",
  ACTIVITY_STEPS: "measurements.typeSteps",
  BLOOD_GLUCOSE: "measurements.typeBloodGlucose",
+  BLOOD_KETONES: "measurements.typeBloodKetones",
  TOTAL_BODY_WATER: "measurements.typeTotalBodyWater",
  BONE_MASS: "measurements.typeBoneMass",
  OXYGEN_SATURATION: "measurements.typeOxygenSaturation",
@@ -21,6 +21,7 @@ const unitMap: Record<string, string> = {
  SLEEP_DURATION: "minutes",
  ACTIVITY_STEPS: "steps",
  BLOOD_GLUCOSE: "mg/dL",
+  BLOOD_KETONES: "mmol/L",
  TOTAL_BODY_WATER: "kg",
  BONE_MASS: "kg",
  OXYGEN_SATURATION: "%",
@@ -20,6 +20,12 @@ export const VALUE_RANGES: Record<string, { min: number; max: number }> = {
  SLEEP_DURATION: { min: 0, max: 1440 },
  ACTIVITY_STEPS: { min: 0, max: 200000 },
  BLOOD_GLUCOSE: { min: 20, max: 800 }, // mg/dL — covers severe hypo to severe hyperglycemia
+  // Beta-hydroxybutyrate, mmol/L. The blood ketone meters people type these
+  // off (Abbott Precision Xtra / FreeStyle Optium, Keto-Mojo, Nova Max Plus)
+  // measure from 0.0 or 0.1 up to 8.0 mmol/L and print "HI" above it; 10
+  // leaves room for a venous value read off a lab sheet. A meter reads 0.0,
+  // so zero is a real reading, not an empty one.
+  BLOOD_KETONES: { min: 0, max: 10 },
  TOTAL_BODY_WATER: { min: 5, max: 100 }, // kg of water — adults typically 30–55 kg
  BONE_MASS: { min: 0.5, max: 8 }, // kg — adult plausibility (typical 2.5–4.5 kg)
  // Pulse oximetry (SpO2). BTS Guideline 2017 + ATS clinical practice put the
@@ -105,6 +105,10 @@ const METRIC_STATUS_MODULE_OWNERS: Partial<Record<MeasurementType, ModuleKey>> =
    STRESS_LEVEL: "recovery",
    TRAINING_READINESS: "recovery",
    CARDIO_RECOVERY: "recovery",
+    // Blood ketones are read off the same meter as fingerstick glucose and
+    // belong to the glucose module; they stay off the Coach snapshot, so the
+    // scope token cannot reach them.
+    BLOOD_KETONES: "glucose",
    // The HRV fallback type. `resolveRichMetricForUser` swaps HRV to its RMSSD
    // fallback for an account that only has ring/strap nightly RMSSD rows, so
    // leaving this unowned would have let the fallback path serve exactly the
@@ -98,6 +98,7 @@ const STATIC_SURFACE_MODULE = {
  // The per-night breathing-disturbance index is a sleep-page signal.
  "insights-page:breathing-disturbances": "sleep",
  "insights-page:blood-glucose": "glucose",
+  "insights-page:ketones": "glucose",
  "insights-page:workouts": "workouts",
  "insights-page:nutrients": "nutrients",
  // Medications is surface-gated by design: its data routes stay open so an
@@ -160,6 +161,8 @@ const STATIC_SURFACE_MODULE = {
  // ── Dashboard summary keys ──
  "summary:SLEEP_DURATION": "sleep",
  "summary:BLOOD_GLUCOSE": "glucose",
+  // Blood ketones sit beside glucose: same meter, same module.
+  "summary:BLOOD_KETONES": "glucose",
  "summary:CARDIO_RECOVERY": "recovery",
  // The recovery module owns the resting_hr domain (`measurement-scope.ts`),
  // so the server gates the type on it; the form and the dashboard follow.
@@ -696,6 +696,8 @@ const seriesKindEnum = z.enum([
  "restingHeartRate",
  "heartRateVariability",
  "vo2Max",
+  "ketones",
+  "glucoseKetoneIndex",
 ]);

 const seriesQuerySchema = z.object({
@@ -747,6 +749,23 @@ const seriesPointSchema = z.object({
    .describe(
      "v1.19.2 (iOS #34 extension) — per-point MAXIMUM for `kind=pulse`. On an aggregated hourly heart-rate bucket `value` is the hour's average and this is the hour's high; null on a per-sample PULSE row and absent for every other kind.",
    ),
+  gki: z
+    .object({
+      glucoseId: z.string().describe("The paired glucose reading's id."),
+      glucoseAt: isoDateTime().describe(
+        "The paired glucose reading's timestamp.",
+      ),
+      glucoseMmol: z
+        .number()
+        .describe("The paired glucose in mmol/L, one decimal."),
+      ketonesMmol: z
+        .number()
+        .describe("The ketone reading (beta-hydroxybutyrate), mmol/L."),
+    })
+    .optional()
+    .describe(
+      "#1367 — for `kind=glucoseKetoneIndex` only: the readings the index was computed from. `id` and `at` are the ketone reading's. Absent for every other kind.",
+    ),
 });

 const seriesResponse = z
@@ -755,7 +774,7 @@ const seriesResponse = z
    unit: z
      .string()
      .describe(
-        "Resolved unit token for `value`. `glucose` follows the user's mg/dL|mmol/L preference; `sleep` is `h` (per-night time-asleep in hours).",
+        "Resolved unit token for `value`. `glucose` follows the user's mg/dL|mmol/L preference; `sleep` is `h` (per-night time-asleep in hours); `ketones` is `mmol/L`; `glucoseKetoneIndex` is `ratio`.",
      ),
    points: z.array(seriesPointSchema),
    stats: z
@@ -783,7 +802,7 @@ const seriesResponse = z
  .meta({
    id: "MeasurementsSeriesResponse",
    description:
-      "iOS-friendly per-kind time series: one point per reading (or per reconstructed night for `sleep`), an explicit `unit` token, and a summary `stats` block. Sample-dense kinds (`pulse`, `glucose`, `heartRateVariability`, `oxygenSaturation`) are bucketed server-side: beyond 90 days per local day, and within 90 days per local hour when the window holds more than 10 000 readings (a continuous glucose sensor, a watch or ring recording every minute; a cuff, a fingerstick meter or a few readings a night stay raw). A bucket carries the mean as `value` and otherwise has the shape of a reading of its kind; a `pulse` bucket also carries its range as `valueMin` / `valueMax`, and a `glucose` bucket is converted to the user's unit like a raw reading. `stats` is always computed over the underlying readings, never over the buckets.",
+      "iOS-friendly per-kind time series: one point per reading (or per reconstructed night for `sleep`), an explicit `unit` token, and a summary `stats` block. Sample-dense kinds (`pulse`, `glucose`, `heartRateVariability`, `oxygenSaturation`) are bucketed server-side: beyond 90 days per local day, and within 90 days per local hour when the window holds more than 10 000 readings (a continuous glucose sensor, a watch or ring recording every minute; a cuff, a fingerstick meter or a few readings a night stay raw). A bucket carries the mean as `value` and otherwise has the shape of a reading of its kind; a `pulse` bucket also carries its range as `valueMin` / `valueMax`, and a `glucose` bucket is converted to the user's unit like a raw reading. `stats` is always computed over the underlying readings, never over the buckets. `glucoseKetoneIndex` (#1367) is derived at read time, never stored: one point per ketone reading above zero that has a glucose reading at the same instant or, failing that, the nearest one within 15 minutes either side; value = glucose (mmol/L, from mg/dL by 18.0182) / ketones (mmol/L), one decimal. Draw it as given; do not recompute it.",
  });

 // ── Batched daily series (v1.18.6 dashboard fetch coalescing) ────────
@@ -175,10 +175,11 @@ export function getPRDirection(
      if (context.weightGoal === "higher") return PersonalRecordDirection.MAX;
      return null;

-    // Explicitly no PersonalRecord — see comment block above.
+    // Explicitly no PersonalRecord (see above); ketones follow a clinician's plan.
    case "BLOOD_PRESSURE_SYS":
    case "BLOOD_PRESSURE_DIA":
    case "BLOOD_GLUCOSE":
+    case "BLOOD_KETONES":
    case "BODY_TEMPERATURE":
    case "SKIN_TEMPERATURE":
    case "PULSE":
@@ -267,9 +268,8 @@ export function getPRDirection(
    case "TRAINING_READINESS":
    case "ACUTE_TRAINING_LOAD":
    // v1.17.1 — Oura coverage. The Sleep Score is a nightly derived composite
-    // (like the other sleep-quality indices), and the body-temperature
-    // deviation is a homeostatic signed offset centred on 0 — neither has a
-    // goal axis, so both stay null like the rest of the derived/homeostatic set.
+    // and the body-temperature deviation a homeostatic signed offset centred
+    // on 0: neither has a goal axis, so both stay null like the set above.
    case "SLEEP_SCORE":
    case "BODY_TEMPERATURE_DEVIATION":
    // v1.19.0 — Oura resilience. An ordinal-encoded categorical band
@@ -0,0 +1,50 @@
+"use client";
+
+import { useQuery } from "@tanstack/react-query";
+
+import { useAuth } from "@/hooks/use-auth";
+import { apiGet } from "@/lib/api/api-fetch";
+import { queryKeys } from "@/lib/query-keys";
+
+/** One point of `kind=glucoseKetoneIndex`, as the server resolved it. */
+export interface GlucoseKetoneIndexSeriesPoint {
+  /** The ketone reading's id. */
+  id: string;
+  /** The ketone reading's instant. */
+  at: string;
+  /** The index, one decimal. */
+  value: number;
+  gki: {
+    glucoseId: string;
+    glucoseAt: string;
+    glucoseMmol: number;
+    ketonesMmol: number;
+  };
+}
+
+interface GlucoseKetoneIndexSeries {
+  kind: "glucoseKetoneIndex";
+  unit: string;
+  points: GlucoseKetoneIndexSeriesPoint[];
+}
+
+/** The whole history the series route serves; the chart narrows it. */
+export const GKI_SERIES_DAYS = 3650;
+
+/**
+ * The glucose-ketone index over the last {@link GKI_SERIES_DAYS} days (#1367).
+ * The server pairs the readings and computes every index; the card draws them
+ * as given.
+ */
+export function useGlucoseKetoneIndexSeries() {
+  const { isAuthenticated } = useAuth();
+  return useQuery({
+    queryKey: queryKeys.glucoseKetoneIndexSeries(GKI_SERIES_DAYS),
+    queryFn: () =>
+      apiGet<GlucoseKetoneIndexSeries>(
+        `/api/measurements/series?kind=glucoseKetoneIndex&days=${GKI_SERIES_DAYS}`,
+      ),
+    staleTime: 60_000,
+    enabled: isAuthenticated,
+  });
+}
@@ -127,6 +127,14 @@ export const measurementKeys = {
  bpTimeOfDay: (days: number) =>
    ["measurements", "bp-time-of-day", days] as const,

+  /**
+   * #1367 — the glucose-ketone index series
+   * (`GET /api/measurements/series?kind=glucoseKetoneIndex&days=`). Under the
+   * `["measurements"]` prefix, so a new glucose or ketone reading refreshes it.
+   */
+  glucoseKetoneIndexSeries: (days: number) =>
+    ["measurements", "glucose-ketone-index", days] as const,
+
  /**
   * v1.8.5 — bounded recent-timestamp read powering the
   * measurement-diversity nudge on an insights category page. Keyed by
@@ -63,9 +63,9 @@ function resolves(key: string): boolean {

 describe("report selection catalogue", () => {
  it("carries every measurement type and every structured leaf", () => {
-    expect(MEASUREMENT_LEAF_IDS).toHaveLength(91);
+    expect(MEASUREMENT_LEAF_IDS).toHaveLength(92);
    expect(STRUCTURED_LEAF_IDS).toHaveLength(20);
-    expect(ALL_LEAF_IDS).toHaveLength(111);
+    expect(ALL_LEAF_IDS).toHaveLength(112);
  });

  it("resolves a label for every leaf", () => {
@@ -197,6 +197,7 @@ export const MEASUREMENT_LEAF_GROUP: Record<MeasurementType, ReportGroupId> = {

  // ── glucose ──
  BLOOD_GLUCOSE: "glucose",
+  BLOOD_KETONES: "glucose",

  // ── fenced ──
  // Mindful minutes and the State of Mind valence are mental-health
@@ -337,6 +338,7 @@ export const LEAF_MODULE: Partial<Record<ReportLeafId, ModuleKey>> = {
  INDOOR_HUMIDITY: "environment",
  // Glucose: the raw series and the derived panel.
  BLOOD_GLUCOSE: "glucose",
+  BLOOD_KETONES: "glucose",
  GLUCOSE_PANEL: "glucose",
  // The screening totals ride the mental-health module as well as being
  // fenced in the panel. Item-level answers are never a Measurement, so only
@@ -328,5 +328,11 @@
    "display": "Indoor relative humidity",
    "unit": "%",
    "category": "activity"
+  },
+  "BLOOD_KETONES": {
+    "loinc": "104816-4",
+    "display": "Beta hydroxybutyrate [Moles/volume] in Blood",
+    "unit": "mmol/L",
+    "category": "laboratory"
  }
 }
@@ -341,6 +341,35 @@ export const SIGNALS: Record<string, SignalDefinition> = {
      mcp: true,
    },
  },
+  // Blood ketones (#1367). Beta-hydroxybutyrate from a fingerstick meter,
+  // typed by hand. No band: what a ketone reading should be depends on the
+  // plan a clinician sets, so the value is shown as recorded. Off the Coach
+  // snapshot and the correlations, readable over MCP.
+  BLOOD_KETONES: {
+    key: "BLOOD_KETONES",
+    kind: "measurement",
+    source: { measurementType: "BLOOD_KETONES" },
+    displayName: "Blood ketones (BHB)",
+    unit: "mmol/L",
+    direction: "target-band",
+    archetype: "physiological-vital",
+    surfaces: {
+      detailPage: true,
+      correlationEligible: false,
+      coachSnapshot: false,
+      mcp: true,
+    },
+    // LOINC 104816-4 "Beta hydroxybutyrate [Moles/volume] in Blood": the
+    // quantitative, method-less blood term. A typed value does not say
+    // whether it came from a strip or a venous draw, and the strip term
+    // (66441-7) is semi-quantitative, which a numeric mmol/L reading is not.
+    fhir: {
+      loinc: "104816-4",
+      display: "Beta hydroxybutyrate [Moles/volume] in Blood",
+      unit: "mmol/L",
+      category: "laboratory",
+    },
+  },
  WALKING_HEART_RATE_AVERAGE: {
    key: "WALKING_HEART_RATE_AVERAGE",
    kind: "measurement",
@@ -171,6 +171,8 @@ export const measurementTypeEnum = z.enum([
  "ACUTE_TRAINING_LOAD",
  // ── resting energy (#1340), HealthKit `basalEnergyBurned` ──
  "BASAL_ENERGY_BURNED",
+  // ── blood ketones (#1367), beta-hydroxybutyrate in mmol/L ──
+  "BLOOD_KETONES",
 ]);

 /**
@@ -68,7 +68,7 @@
          "backupId": "<id:1>",
          "ownerId": "round-trip-owner",
          "reason": "schema_invalid",
-          "message": "measurements.0.type: Invalid option: expected one of \"WEIGHT\"|\"BLOOD_PRESSURE_SYS\"|\"BLOOD_PRESSURE_DIA\"|\"PULSE\"|\"BODY_FAT\"|\"SLEEP_DURATION\"|\"ACTIVITY_STEPS\"|\"BLOOD_GLUCOSE\"|\"TOTAL_BODY_WATER\"|\"BONE_MASS\"|\"OXYGEN_SATURATION\"|\"HEART_RATE_VARIABILITY\"|\"RESTING_HEART_RATE\"|\"ACTIVE_ENERGY_BURNED\"|\"FLIGHTS_CLIMBED\"|\"WALKING_RUNNING_DISTANCE\"|\"VO2_MAX\"|\"BODY_TEMPERATURE\"|\"FAT_FREE_MASS\"|\"FAT_MASS\"|\"MUSCLE_MASS\"|\"SKIN_TEMPERATURE\"|\"PULSE_WAVE_VELOCITY\"|\"VASCULAR_AGE\"|\"VISCERAL_FAT\"|\"AUDIO_EXPOSURE_ENV\"|\"AUDIO_EXPOSURE_HEADPHONE\"|\"TIME_IN_DAYLIGHT\"|\"WALKING_STEADINESS\"|\"AUDIO_EXPOSURE_EVENT\"|\"RESPIRATORY_RATE\"|\"BODY_MASS_INDEX\"|\"LEAN_BODY_MASS\"|\"WALKING_HEART_RATE_AVERAGE\"|\"WALKING_ASYMMETRY\"|\"WALKING_DOUBLE_SUPPORT\"|\"WALKING_STEP_LENGTH\"|\"WALKING_SPEED\"|\"CARDIO_RECOVERY\"|\"WRIST_TEMPERATURE\"|\"FALL_COUNT\"|\"SIX_MINUTE_WALK_DISTANCE\"|\"STAIR_ASCENT_SPEED\"|\"STAIR_DESCENT_SPEED\"|\"BREATHING_DISTURBANCES\"|\"IRREGULAR_RHYTHM_NOTIFICATION\"|\"HIGH_HEART_RATE_EVENT\"|\"LOW_HEART_RATE_EVENT\"|\"WALKING_STEADINESS_EVENT\"|\"BREATHING_DISTURBANCE_EVENT\"|\"RECOVERY_SCORE\"|\"STRESS_SCORE\"|\"STRAIN_SCORE\"|\"HRV_RMSSD\"|\"DAY_STRAIN\"|\"WORKOUT_STRAIN\"|\"SLEEP_PERFORMANCE\"|\"SLEEP_EFFICIENCY\"|\"SLEEP_CONSISTENCY\"|\"SLEEP_NEED\"|\"ENERGY_EXPENDITURE_KJ\"|\"AVERAGE_HEART_RATE\"|\"MAX_HEART_RATE\"|\"SLEEP_DISTURBANCE_COUNT\"|\"ANS_CHARGE\"|\"CARDIO_LOAD\"|\"SLEEP_SCORE\"|\"BODY_TEMPERATURE_DEVIATION\"|\"RESILIENCE\"|\"PHQ9_SCORE\"|\"GAD7_SCORE\"|\"GRIP_STRENGTH\"|\"PAIN_NRS\"|\"WAIST_CIRCUMFERENCE\"|\"WAIST_TO_HEIGHT\"|\"WHO5_SCORE\"|\"SCI_SCORE\"|\"EXERCISE_MINUTES\"|\"STAND_MINUTES\"|\"STAND_HOURS\"|\"MINDFUL_MINUTES\"|\"STATE_OF_MIND_VALENCE\"|\"INDOOR_CO2\"|\"INDOOR_TEMPERATURE\"|\"INDOOR_HUMIDITY\"|\"AFIB_BURDEN\"|\"BODY_BATTERY\"|\"STRESS_LEVEL\"|\"TRAINING_READINESS\"|\"ACUTE_TRAINING_LOAD\"|\"BASAL_ENERGY_BURNED\""
+          "message": "measurements.0.type: Invalid option: expected one of \"WEIGHT\"|\"BLOOD_PRESSURE_SYS\"|\"BLOOD_PRESSURE_DIA\"|\"PULSE\"|\"BODY_FAT\"|\"SLEEP_DURATION\"|\"ACTIVITY_STEPS\"|\"BLOOD_GLUCOSE\"|\"TOTAL_BODY_WATER\"|\"BONE_MASS\"|\"OXYGEN_SATURATION\"|\"HEART_RATE_VARIABILITY\"|\"RESTING_HEART_RATE\"|\"ACTIVE_ENERGY_BURNED\"|\"FLIGHTS_CLIMBED\"|\"WALKING_RUNNING_DISTANCE\"|\"VO2_MAX\"|\"BODY_TEMPERATURE\"|\"FAT_FREE_MASS\"|\"FAT_MASS\"|\"MUSCLE_MASS\"|\"SKIN_TEMPERATURE\"|\"PULSE_WAVE_VELOCITY\"|\"VASCULAR_AGE\"|\"VISCERAL_FAT\"|\"AUDIO_EXPOSURE_ENV\"|\"AUDIO_EXPOSURE_HEADPHONE\"|\"TIME_IN_DAYLIGHT\"|\"WALKING_STEADINESS\"|\"AUDIO_EXPOSURE_EVENT\"|\"RESPIRATORY_RATE\"|\"BODY_MASS_INDEX\"|\"LEAN_BODY_MASS\"|\"WALKING_HEART_RATE_AVERAGE\"|\"WALKING_ASYMMETRY\"|\"WALKING_DOUBLE_SUPPORT\"|\"WALKING_STEP_LENGTH\"|\"WALKING_SPEED\"|\"CARDIO_RECOVERY\"|\"WRIST_TEMPERATURE\"|\"FALL_COUNT\"|\"SIX_MINUTE_WALK_DISTANCE\"|\"STAIR_ASCENT_SPEED\"|\"STAIR_DESCENT_SPEED\"|\"BREATHING_DISTURBANCES\"|\"IRREGULAR_RHYTHM_NOTIFICATION\"|\"HIGH_HEART_RATE_EVENT\"|\"LOW_HEART_RATE_EVENT\"|\"WALKING_STEADINESS_EVENT\"|\"BREATHING_DISTURBANCE_EVENT\"|\"RECOVERY_SCORE\"|\"STRESS_SCORE\"|\"STRAIN_SCORE\"|\"HRV_RMSSD\"|\"DAY_STRAIN\"|\"WORKOUT_STRAIN\"|\"SLEEP_PERFORMANCE\"|\"SLEEP_EFFICIENCY\"|\"SLEEP_CONSISTENCY\"|\"SLEEP_NEED\"|\"ENERGY_EXPENDITURE_KJ\"|\"AVERAGE_HEART_RATE\"|\"MAX_HEART_RATE\"|\"SLEEP_DISTURBANCE_COUNT\"|\"ANS_CHARGE\"|\"CARDIO_LOAD\"|\"SLEEP_SCORE\"|\"BODY_TEMPERATURE_DEVIATION\"|\"RESILIENCE\"|\"PHQ9_SCORE\"|\"GAD7_SCORE\"|\"GRIP_STRENGTH\"|\"PAIN_NRS\"|\"WAIST_CIRCUMFERENCE\"|\"WAIST_TO_HEIGHT\"|\"WHO5_SCORE\"|\"SCI_SCORE\"|\"EXERCISE_MINUTES\"|\"STAND_MINUTES\"|\"STAND_HOURS\"|\"MINDFUL_MINUTES\"|\"STATE_OF_MIND_VALENCE\"|\"INDOOR_CO2\"|\"INDOOR_TEMPERATURE\"|\"INDOOR_HUMIDITY\"|\"AFIB_BURDEN\"|\"BODY_BATTERY\"|\"STRESS_LEVEL\"|\"TRAINING_READINESS\"|\"ACUTE_TRAINING_LOAD\"|\"BASAL_ENERGY_BURNED\"|\"BLOOD_KETONES\""
        }
      }
    ],
@@ -0,0 +1,339 @@
+/**
+ * Blood ketones and the glucose-ketone index (#1367), against real Postgres.
+ *
+ * A fingerstick posts its glucose and ketones as one array: both rows land
+ * with one timestamp, or neither does. The index is derived at read time by
+ * one pairing rule and reaches the series route, the day and the doctor
+ * report with the same numbers; a ketone reading without a glucose reading
+ * within 15 minutes, or with a value of zero, has none.
+ */
+import { NextRequest } from "next/server";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+process.env.ENCRYPTION_KEY =
+  "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef";
+
+import { collectDoctorReportData } from "@/lib/doctor-report-data";
+import { readGlucoseKetoneIndex } from "@/lib/measurements/read-glucose-ketone-index";
+import { selectionFromLeaves } from "@/lib/report-selection/selection";
+
+import { cookieJar, headerJar } from "./mock-next-headers";
+import { getPrismaClient, truncateAllTables } from "./setup";
+
+vi.mock("next/headers", async () => {
+  const { cookieJar, headerJar } = await import("./mock-next-headers");
+  return {
+    headers: vi.fn(async () => ({
+      get: (name: string) => headerJar.get(name.toLowerCase()) ?? null,
+    })),
+    cookies: vi.fn(async () => ({
+      get: (name: string) => {
+        const value = cookieJar.get(name);
+        return value ? { name, value } : undefined;
+      },
+      set: (name: string, value: string) => cookieJar.set(name, value),
+      delete: (name: string) => cookieJar.delete(name),
+    })),
+  };
+});
+
+vi.mock("@/lib/cache/invalidate", async (importOriginal) => {
+  const actual =
+    await importOriginal<typeof import("@/lib/cache/invalidate")>();
+  return { ...actual, invalidateUserData: vi.fn() };
+});
+
+beforeEach(async () => {
+  await truncateAllTables(getPrismaClient());
+  cookieJar.clear();
+  headerJar.clear();
+});
+
+async function signIn(): Promise<string> {
+  const prisma = getPrismaClient();
+  const owner = await prisma.user.create({
+    data: {
+      username: "ketones-owner",
+      email: "ketones-owner@example.test",
+      timezone: "UTC",
+    },
+  });
+  const session = await prisma.session.create({
+    data: { userId: owner.id, expiresAt: new Date(Date.now() + 3_600_000) },
+  });
+  cookieJar.set("healthlog_session", session.id);
+  return owner.id;
+}
+
+function post(body: unknown): NextRequest {
+  return new NextRequest("http://localhost/api/measurements", {
+    method: "POST",
+    headers: { "content-type": "application/json" },
+    body: JSON.stringify(body),
+  });
+}
+
+const MIN = 60_000;
+/** A recent morning, inside every default read window. */
+const T0 = new Date(Date.now() - 2 * 86_400_000);
+T0.setUTCHours(8, 0, 0, 0);
+const at = (offsetMin: number) => new Date(T0.getTime() + offsetMin * MIN);
+
+async function seed(
+  userId: string,
+  rows: Array<{
+    type: "BLOOD_GLUCOSE" | "BLOOD_KETONES";
+    value: number;
+    offsetMin: number;
+  }>,
+) {
+  await getPrismaClient().measurement.createMany({
+    data: rows.map((r) => ({
+      userId,
+      type: r.type,
+      value: r.value,
+      unit: r.type === "BLOOD_GLUCOSE" ? "mg/dL" : "mmol/L",
+      source: "MANUAL" as const,
+      measuredAt: at(r.offsetMin),
+      glucoseContext: r.type === "BLOOD_GLUCOSE" ? ("FASTING" as const) : null,
+    })),
+  });
+}
+
+/**
+ * Four fingersticks: an exact pair, a pair ten minutes apart, a ketone
+ * reading whose glucose is twenty minutes away, and a ketone reading of 0.
+ */
+async function seedMorning(userId: string) {
+  await seed(userId, [
+    { type: "BLOOD_GLUCOSE", value: 81, offsetMin: 0 },
+    { type: "BLOOD_KETONES", value: 1.2, offsetMin: 0 },
+    { type: "BLOOD_GLUCOSE", value: 90, offsetMin: 130 },
+    { type: "BLOOD_KETONES", value: 2, offsetMin: 120 },
+    { type: "BLOOD_GLUCOSE", value: 100, offsetMin: 260 },
+    { type: "BLOOD_KETONES", value: 1.5, offsetMin: 240 },
+    { type: "BLOOD_GLUCOSE", value: 95, offsetMin: 360 },
+    { type: "BLOOD_KETONES", value: 0, offsetMin: 360 },
+  ]);
+}
+
+describe("fingerstick entry (#1367)", () => {
+  it("writes the glucose and the ketones together with one timestamp", async () => {
+    const userId = await signIn();
+    const { POST } = await import("@/app/api/measurements/route");
+    const measuredAt = at(0).toISOString();
+    const res = await POST(
+      post([
+        {
+          type: "BLOOD_GLUCOSE",
+          value: 81,
+          measuredAt,
+          glucoseContext: "FASTING",
+        },
+        { type: "BLOOD_KETONES", value: 1.2, measuredAt },
+      ]),
+    );
+    expect(res.status).toBe(201);
+    const rows = await getPrismaClient().measurement.findMany({
+      where: { userId },
+      orderBy: { type: "asc" },
+      select: { type: true, value: true, unit: true, measuredAt: true },
+    });
+    expect(rows).toEqual([
+      { type: "BLOOD_GLUCOSE", value: 81, unit: "mg/dL", measuredAt: at(0) },
+      { type: "BLOOD_KETONES", value: 1.2, unit: "mmol/L", measuredAt: at(0) },
+    ]);
+  });
+
+  it("writes neither reading when the ketones are out of range", async () => {
+    const userId = await signIn();
+    const { POST } = await import("@/app/api/measurements/route");
+    const measuredAt = at(0).toISOString();
+    const res = await POST(
+      post([
+        {
+          type: "BLOOD_GLUCOSE",
+          value: 81,
+          measuredAt,
+          glucoseContext: "FASTING",
+        },
+        { type: "BLOOD_KETONES", value: 12, measuredAt },
+      ]),
+    );
+    expect(res.status).toBe(422);
+    expect(
+      await getPrismaClient().measurement.count({ where: { userId } }),
+    ).toBe(0);
+  });
+
+  it("rolls the ketones back when the glucose half is a duplicate", async () => {
+    const userId = await signIn();
+    const { POST } = await import("@/app/api/measurements/route");
+    const measuredAt = at(0).toISOString();
+    const glucose = {
+      type: "BLOOD_GLUCOSE",
+      value: 81,
+      measuredAt,
+      glucoseContext: "FASTING",
+    };
+    expect((await POST(post(glucose))).status).toBe(201);
+    const res = await POST(
+      post([glucose, { type: "BLOOD_KETONES", value: 1.2, measuredAt }]),
+    );
+    expect(res.status).toBe(409);
+    expect(
+      await getPrismaClient().measurement.count({
+        where: { userId, type: "BLOOD_KETONES" },
+      }),
+    ).toBe(0);
+  });
+});
+
+describe("glucose-ketone index (#1367)", () => {
+  it("pairs by the one rule and leaves out what has no partner", async () => {
+    const userId = await signIn();
+    await seedMorning(userId);
+    const points = await readGlucoseKetoneIndex({
+      userId,
+      from: at(-60),
+      to: at(24 * 60),
+    });
+    expect(
+      points.map((p) => ({
+        at: p.at,
+        glucoseAt: p.glucoseAt,
+        value: p.value,
+        ketonesMmol: p.ketonesMmol,
+        glucoseMmol: p.glucoseMmol,
+      })),
+    ).toEqual([
+      // 81 mg/dL = 4.5 mmol/L; / 1.2 = 3.7
+      {
+        at: at(0).toISOString(),
+        glucoseAt: at(0).toISOString(),
+        value: 3.7,
+        ketonesMmol: 1.2,
+        glucoseMmol: 4.5,
+      },
+      // 90 mg/dL = 5.0 mmol/L, ten minutes later; / 2 = 2.5
+      {
+        at: at(120).toISOString(),
+        glucoseAt: at(130).toISOString(),
+        value: 2.5,
+        ketonesMmol: 2,
+        glucoseMmol: 5,
+      },
+    ]);
+  });
+
+  it("pairs a glucose reading just outside the window with a ketone reading just inside it", async () => {
+    const userId = await signIn();
+    await seed(userId, [
+      { type: "BLOOD_GLUCOSE", value: 90, offsetMin: -5 },
+      { type: "BLOOD_KETONES", value: 1, offsetMin: 0 },
+    ]);
+    const points = await readGlucoseKetoneIndex({
+      userId,
+      from: at(0),
+      to: at(60),
+    });
+    expect(points.map((p) => p.glucoseAt)).toEqual([at(-5).toISOString()]);
+  });
+
+  it("serves the index and the ketones on the series route", async () => {
+    await signIn().then(seedMorning);
+    const { GET } = await import("@/app/api/measurements/series/route");
+    const gki = await GET(
+      new NextRequest(
+        "http://localhost/api/measurements/series?kind=glucoseKetoneIndex&days=30",
+      ),
+    );
+    expect(gki.status).toBe(200);
+    const gkiBody = (await gki.json()) as {
+      data: {
+        unit: string;
+        points: Array<{
+          value: number;
+          gki: { glucoseAt: string; glucoseMmol: number; ketonesMmol: number };
+        }>;
+        stats: { count: number };
+        referenceLines: unknown[];
+      };
+    };
+    expect(gkiBody.data.unit).toBe("ratio");
+    expect(gkiBody.data.points.map((p) => p.value)).toEqual([3.7, 2.5]);
+    expect(gkiBody.data.points[1]!.gki).toMatchObject({
+      glucoseAt: at(130).toISOString(),
+      glucoseMmol: 5,
+      ketonesMmol: 2,
+    });
+    expect(gkiBody.data.stats.count).toBe(2);
+    expect(gkiBody.data.referenceLines).toEqual([]);
+
+    const ketones = await GET(
+      new NextRequest(
+        "http://localhost/api/measurements/series?kind=ketones&days=30",
+      ),
+    );
+    expect(ketones.status).toBe(200);
+    const ketoneBody = (await ketones.json()) as {
+      data: { unit: string; points: Array<{ value: number }> };
+    };
+    expect(ketoneBody.data.unit).toBe("mmol/L");
+    expect(ketoneBody.data.points.map((p) => p.value)).toEqual([
+      1.2, 2, 1.5, 0,
+    ]);
+  });
+
+  it("carries the day's index on the day", async () => {
+    await signIn().then(seedMorning);
+    const { GET } = await import("@/app/api/day/[date]/route");
+    const date = at(0).toISOString().slice(0, 10);
+    const res = await GET(
+      new Request(`http://localhost/api/day/${date}`) as never,
+      { params: Promise.resolve({ date }) },
+    );
+    expect(res.status).toBe(200);
+    const body = (await res.json()) as {
+      data: {
+        glucoseKetoneIndex?: Array<{ value: number; glucoseAt: string }>;
+        values: Array<{ type: string }>;
+      };
+    };
+    expect(body.data.glucoseKetoneIndex?.map((p) => p.value)).toEqual([
+      3.7, 2.5,
+    ]);
+    expect(body.data.values.some((v) => v.type === "BLOOD_KETONES")).toBe(true);
+  });
+
+  it("puts the index in the doctor report only beside both readings", async () => {
+    const userId = await signIn();
+    await seedMorning(userId);
+    const range = {
+      start: at(-24 * 60),
+      end: at(24 * 60),
+      days: 2,
+    };
+    const both = await collectDoctorReportData(
+      userId,
+      range,
+      selectionFromLeaves(["BLOOD_KETONES", "BLOOD_GLUCOSE"]),
+    );
+    expect(both.stats.BLOOD_KETONES?.count).toBe(4);
+    expect(both.glucoseKetoneIndex).toMatchObject({
+      count: 2,
+      latest: 2.5,
+      min: 2.5,
+      max: 3.7,
+      avg: 3.1,
+    });
+
+    const ketonesOnly = await collectDoctorReportData(
+      userId,
+      range,
+      selectionFromLeaves(["BLOOD_KETONES"]),
+    );
+    expect(ketonesOnly.stats.BLOOD_KETONES?.count).toBe(4);
+    expect(ketonesOnly.glucoseKetoneIndex).toBeNull();
+  });
+});
@@ -1357,6 +1357,20 @@
          "slope30": null,
          "avg30LastMonth": null,
          "avg30LastYear": null
+        },
+        "BLOOD_KETONES": {
+          "count": 0,
+          "latest": null,
+          "min": null,
+          "max": null,
+          "mean": null,
+          "median": null,
+          "avg7": null,
+          "avg30": null,
+          "slope7": null,
+          "slope30": null,
+          "avg30LastMonth": null,
+          "avg30LastYear": null
        }
      },
      "bmi": null,
@@ -1484,7 +1498,8 @@
        "STRESS_LEVEL": null,
        "TRAINING_READINESS": null,
        "ACUTE_TRAINING_LOAD": null,
-        "BASAL_ENERGY_BURNED": null
+        "BASAL_ENERGY_BURNED": null,
+        "BLOOD_KETONES": null
      },
      "sleepSourceDiscrepancy": null,
      "recoveryEmpty": "general"
@@ -1357,6 +1357,20 @@
          "slope30": null,
          "avg30LastMonth": null,
          "avg30LastYear": null
+        },
+        "BLOOD_KETONES": {
+          "count": 0,
+          "latest": null,
+          "min": null,
+          "max": null,
+          "mean": null,
+          "median": null,
+          "avg7": null,
+          "avg30": null,
+          "slope7": null,
+          "slope30": null,
+          "avg30LastMonth": null,
+          "avg30LastYear": null
        }
      },
      "bmi": null,
@@ -1484,7 +1498,8 @@
        "STRESS_LEVEL": null,
        "TRAINING_READINESS": null,
        "ACUTE_TRAINING_LOAD": null,
-        "BASAL_ENERGY_BURNED": null
+        "BASAL_ENERGY_BURNED": null,
+        "BLOOD_KETONES": null
      },
      "sleepSourceDiscrepancy": null,
      "recoveryEmpty": "general"
@@ -1357,6 +1357,20 @@
          "slope30": null,
          "avg30LastMonth": null,
          "avg30LastYear": null
+        },
+        "BLOOD_KETONES": {
+          "count": 0,
+          "latest": null,
+          "min": null,
+          "max": null,
+          "mean": null,
+          "median": null,
+          "avg7": null,
+          "avg30": null,
+          "slope7": null,
+          "slope30": null,
+          "avg30LastMonth": null,
+          "avg30LastYear": null
        }
      },
      "bmi": 25.9,
@@ -2500,7 +2514,8 @@
        "STRESS_LEVEL": null,
        "TRAINING_READINESS": null,
        "ACUTE_TRAINING_LOAD": null,
-        "BASAL_ENERGY_BURNED": null
+        "BASAL_ENERGY_BURNED": null,
+        "BLOOD_KETONES": null
      }
    },
    "error": null
@@ -1357,6 +1357,20 @@
          "slope30": null,
          "avg30LastMonth": null,
          "avg30LastYear": null
+        },
+        "BLOOD_KETONES": {
+          "count": 0,
+          "latest": null,
+          "min": null,
+          "max": null,
+          "mean": null,
+          "median": null,
+          "avg7": null,
+          "avg30": null,
+          "slope7": null,
+          "slope30": null,
+          "avg30LastMonth": null,
+          "avg30LastYear": null
        }
      },
      "bmi": 25.9,
@@ -2500,7 +2514,8 @@
        "STRESS_LEVEL": null,
        "TRAINING_READINESS": null,
        "ACUTE_TRAINING_LOAD": null,
-        "BASAL_ENERGY_BURNED": null
+        "BASAL_ENERGY_BURNED": null,
+        "BLOOD_KETONES": null
      }
    },
    "error": null
@@ -1277,6 +1277,20 @@
          "slope30": null,
          "avg30LastMonth": null,
          "avg30LastYear": null
+        },
+        "BLOOD_KETONES": {
+          "count": 0,
+          "latest": null,
+          "min": null,
+          "max": null,
+          "mean": null,
+          "median": null,
+          "avg7": null,
+          "avg30": null,
+          "slope7": null,
+          "slope30": null,
+          "avg30LastMonth": null,
+          "avg30LastYear": null
        }
      },
      "bmi": null,
@@ -1647,7 +1661,8 @@
        "STRESS_LEVEL": null,
        "TRAINING_READINESS": null,
        "ACUTE_TRAINING_LOAD": null,
-        "BASAL_ENERGY_BURNED": null
+        "BASAL_ENERGY_BURNED": null,
+        "BLOOD_KETONES": null
      }
    },
    "error": null
@@ -8,7 +8,7 @@
        {
          "path": "kind",
          "code": "invalid_value",
-          "message": "Invalid option: expected one of \"weight\"|\"bloodPressure\"|\"pulse\"|\"bodyFat\"|\"glucose\"|\"sleep\"|\"steps\"|\"totalBodyWater\"|\"boneMass\"|\"oxygenSaturation\"|\"restingHeartRate\"|\"heartRateVariability\"|\"vo2Max\""
+          "message": "Invalid option: expected one of \"weight\"|\"bloodPressure\"|\"pulse\"|\"bodyFat\"|\"glucose\"|\"sleep\"|\"steps\"|\"totalBodyWater\"|\"boneMass\"|\"oxygenSaturation\"|\"restingHeartRate\"|\"heartRateVariability\"|\"vo2Max\"|\"ketones\"|\"glucoseKetoneIndex\""
        },
        {
          "path": "days",
@@ -39,7 +39,7 @@
          {
            "path": "kind",
            "code": "invalid_value",
-            "message": "Invalid option: expected one of \"weight\"|\"bloodPressure\"|\"pulse\"|\"bodyFat\"|\"glucose\"|\"sleep\"|\"steps\"|\"totalBodyWater\"|\"boneMass\"|\"oxygenSaturation\"|\"restingHeartRate\"|\"heartRateVariability\"|\"vo2Max\""
+            "message": "Invalid option: expected one of \"weight\"|\"bloodPressure\"|\"pulse\"|\"bodyFat\"|\"glucose\"|\"sleep\"|\"steps\"|\"totalBodyWater\"|\"boneMass\"|\"oxygenSaturation\"|\"restingHeartRate\"|\"heartRateVariability\"|\"vo2Max\"|\"ketones\"|\"glucoseKetoneIndex\""
          },
          {
            "path": "days",